feat(backend): add user custom attributes system

Add a flexible user attribute system that allows admins to define
custom fields for users (text, textarea, number, email, url, date,
select, multi_select types).

- Add Ent schemas for UserAttributeDefinition and UserAttributeValue
- Add service layer with validation logic
- Add repository layer with batch operations support
- Add admin API endpoints for CRUD and reorder operations
- Add batch API for loading attribute values for multiple users
- Add database migration (018_user_attributes.sql)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/ent/userattributedefinition/userattributedefinition.go

@@ -0,0 +1,205 @@
+// Code generated by ent, DO NOT EDIT.
+
+package userattributedefinition
+
+import (
+	"time"
+
+	"entgo.io/ent"
+	"entgo.io/ent/dialect/sql"
+	"entgo.io/ent/dialect/sql/sqlgraph"
+)
+
+const (
+	// Label holds the string label denoting the userattributedefinition type in the database.
+	Label = "user_attribute_definition"
+	// FieldID holds the string denoting the id field in the database.
+	FieldID = "id"
+	// FieldCreatedAt holds the string denoting the created_at field in the database.
+	FieldCreatedAt = "created_at"
+	// FieldUpdatedAt holds the string denoting the updated_at field in the database.
+	FieldUpdatedAt = "updated_at"
+	// FieldDeletedAt holds the string denoting the deleted_at field in the database.
+	FieldDeletedAt = "deleted_at"
+	// FieldKey holds the string denoting the key field in the database.
+	FieldKey = "key"
+	// FieldName holds the string denoting the name field in the database.
+	FieldName = "name"
+	// FieldDescription holds the string denoting the description field in the database.
+	FieldDescription = "description"
+	// FieldType holds the string denoting the type field in the database.
+	FieldType = "type"
+	// FieldOptions holds the string denoting the options field in the database.
+	FieldOptions = "options"
+	// FieldRequired holds the string denoting the required field in the database.
+	FieldRequired = "required"
+	// FieldValidation holds the string denoting the validation field in the database.
+	FieldValidation = "validation"
+	// FieldPlaceholder holds the string denoting the placeholder field in the database.
+	FieldPlaceholder = "placeholder"
+	// FieldDisplayOrder holds the string denoting the display_order field in the database.
+	FieldDisplayOrder = "display_order"
+	// FieldEnabled holds the string denoting the enabled field in the database.
+	FieldEnabled = "enabled"
+	// EdgeValues holds the string denoting the values edge name in mutations.
+	EdgeValues = "values"
+	// Table holds the table name of the userattributedefinition in the database.
+	Table = "user_attribute_definitions"
+	// ValuesTable is the table that holds the values relation/edge.
+	ValuesTable = "user_attribute_values"
+	// ValuesInverseTable is the table name for the UserAttributeValue entity.
+	// It exists in this package in order to avoid circular dependency with the "userattributevalue" package.
+	ValuesInverseTable = "user_attribute_values"
+	// ValuesColumn is the table column denoting the values relation/edge.
+	ValuesColumn = "attribute_id"
+)
+
+// Columns holds all SQL columns for userattributedefinition fields.
+var Columns = []string{
+	FieldID,
+	FieldCreatedAt,
+	FieldUpdatedAt,
+	FieldDeletedAt,
+	FieldKey,
+	FieldName,
+	FieldDescription,
+	FieldType,
+	FieldOptions,
+	FieldRequired,
+	FieldValidation,
+	FieldPlaceholder,
+	FieldDisplayOrder,
+	FieldEnabled,
+}
+
+// ValidColumn reports if the column name is valid (part of the table columns).
+func ValidColumn(column string) bool {
+	for i := range Columns {
+		if column == Columns[i] {
+			return true
+		}
+	}
+	return false
+}
+
+// Note that the variables below are initialized by the runtime
+// package on the initialization of the application. Therefore,
+// it should be imported in the main as follows:
+//
+//	import _ "github.com/Wei-Shaw/sub2api/ent/runtime"
+var (
+	Hooks        [1]ent.Hook
+	Interceptors [1]ent.Interceptor
+	// DefaultCreatedAt holds the default value on creation for the "created_at" field.
+	DefaultCreatedAt func() time.Time
+	// DefaultUpdatedAt holds the default value on creation for the "updated_at" field.
+	DefaultUpdatedAt func() time.Time
+	// UpdateDefaultUpdatedAt holds the default value on update for the "updated_at" field.
+	UpdateDefaultUpdatedAt func() time.Time
+	// KeyValidator is a validator for the "key" field. It is called by the builders before save.
+	KeyValidator func(string) error
+	// NameValidator is a validator for the "name" field. It is called by the builders before save.
+	NameValidator func(string) error
+	// DefaultDescription holds the default value on creation for the "description" field.
+	DefaultDescription string
+	// TypeValidator is a validator for the "type" field. It is called by the builders before save.
+	TypeValidator func(string) error
+	// DefaultOptions holds the default value on creation for the "options" field.
+	DefaultOptions []map[string]interface{}
+	// DefaultRequired holds the default value on creation for the "required" field.
+	DefaultRequired bool
+	// DefaultValidation holds the default value on creation for the "validation" field.
+	DefaultValidation map[string]interface{}
+	// DefaultPlaceholder holds the default value on creation for the "placeholder" field.
+	DefaultPlaceholder string
+	// PlaceholderValidator is a validator for the "placeholder" field. It is called by the builders before save.
+	PlaceholderValidator func(string) error
+	// DefaultDisplayOrder holds the default value on creation for the "display_order" field.
+	DefaultDisplayOrder int
+	// DefaultEnabled holds the default value on creation for the "enabled" field.
+	DefaultEnabled bool
+)
+
+// OrderOption defines the ordering options for the UserAttributeDefinition queries.
+type OrderOption func(*sql.Selector)
+
+// ByID orders the results by the id field.
+func ByID(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldID, opts...).ToFunc()
+}
+
+// ByCreatedAt orders the results by the created_at field.
+func ByCreatedAt(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldCreatedAt, opts...).ToFunc()
+}
+
+// ByUpdatedAt orders the results by the updated_at field.
+func ByUpdatedAt(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldUpdatedAt, opts...).ToFunc()
+}
+
+// ByDeletedAt orders the results by the deleted_at field.
+func ByDeletedAt(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldDeletedAt, opts...).ToFunc()
+}
+
+// ByKey orders the results by the key field.
+func ByKey(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldKey, opts...).ToFunc()
+}
+
+// ByName orders the results by the name field.
+func ByName(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldName, opts...).ToFunc()
+}
+
+// ByDescription orders the results by the description field.
+func ByDescription(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldDescription, opts...).ToFunc()
+}
+
+// ByType orders the results by the type field.
+func ByType(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldType, opts...).ToFunc()
+}
+
+// ByRequired orders the results by the required field.
+func ByRequired(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldRequired, opts...).ToFunc()
+}
+
+// ByPlaceholder orders the results by the placeholder field.
+func ByPlaceholder(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldPlaceholder, opts...).ToFunc()
+}
+
+// ByDisplayOrder orders the results by the display_order field.
+func ByDisplayOrder(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldDisplayOrder, opts...).ToFunc()
+}
+
+// ByEnabled orders the results by the enabled field.
+func ByEnabled(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldEnabled, opts...).ToFunc()
+}
+
+// ByValuesCount orders the results by values count.
+func ByValuesCount(opts ...sql.OrderTermOption) OrderOption {
+	return func(s *sql.Selector) {
+		sqlgraph.OrderByNeighborsCount(s, newValuesStep(), opts...)
+	}
+}
+
+// ByValues orders the results by values terms.
+func ByValues(term sql.OrderTerm, terms ...sql.OrderTerm) OrderOption {
+	return func(s *sql.Selector) {
+		sqlgraph.OrderByNeighborTerms(s, newValuesStep(), append([]sql.OrderTerm{term}, terms...)...)
+	}
+}
+func newValuesStep() *sqlgraph.Step {
+	return sqlgraph.NewStep(
+		sqlgraph.From(Table, FieldID),
+		sqlgraph.To(ValuesInverseTable, FieldID),
+		sqlgraph.Edge(sqlgraph.O2M, false, ValuesTable, ValuesColumn),
+	)
+}