refactor: database interaction and error handling (#10762)

This pull request introduces a significant refactoring of the database
interaction layer, focusing on improving explicitness, transactional
control, and error handling. The core change is the removal of the
stateful `QueryExecutor` from repository instances. Instead, it is now
passed as an argument to each method that interacts with the database.

This change makes transaction management more explicit and flexible, as
the same repository instance can be used with a database pool or a
specific transaction without needing to be re-instantiated.

### Key Changes

- **Explicit `QueryExecutor` Passing:**
- All repository methods (`Get`, `List`, `Create`, `Update`, `Delete`,
etc.) in `InstanceRepository`, `OrganizationRepository`,
`UserRepository`, and their sub-repositories now require a
`database.QueryExecutor` (e.g., a `*pgxpool.Pool` or `pgx.Tx`) as the
first argument.
- Repository constructors no longer accept a `QueryExecutor`. For
example, `repository.InstanceRepository(pool)` is now
`repository.InstanceRepository()`.

- **Enhanced Error Handling:**
- A new `database.MissingConditionError` is introduced to enforce
required query conditions, such as ensuring an `instance_id` is always
present in `UPDATE` and `DELETE` operations.
- The database error wrapper in the `postgres` package now correctly
identifies and wraps `pgx.ErrTooManyRows` and similar errors from the
`scany` library into a `database.MultipleRowsFoundError`.

- **Improved Database Conditions:**
- The `database.Condition` interface now includes a
`ContainsColumn(Column) bool` method. This allows for runtime checks to
ensure that critical filters (like `instance_id`) are included in a
query, preventing accidental cross-tenant data modification.
- A new `database.Exists()` condition has been added to support `EXISTS`
subqueries, enabling more complex filtering logic, such as finding an
organization that has a specific domain.

- **Repository and Interface Refactoring:**
- The method for loading related entities (e.g., domains for an
organization) has been changed from a boolean flag (`Domains(true)`) to
a more explicit, chainable method (`LoadDomains()`). This returns a new
repository instance configured to load the sub-resource, promoting
immutability.
- The custom `OrgIdentifierCondition` has been removed in favor of using
the standard `database.Condition` interface, simplifying the API.

- **Code Cleanup and Test Updates:**
  - Unnecessary struct embeddings and metadata have been removed.
- All integration and repository tests have been updated to reflect the
new method signatures, passing the database pool or transaction object
explicitly.
- New tests have been added to cover the new `ExistsDomain`
functionality and other enhancements.

These changes make the data access layer more robust, predictable, and
easier to work with, especially in the context of database transactions.

backend/v3/storage/database/repository/user.go

@@ -12,16 +12,10 @@ const queryUserStmt = `SELECT instance_id, org_id, id, username, type, created_a
 	` first_name, last_name, email_address, email_verified_at, phone_number, phone_verified_at, description` +
 	` FROM users_view users`
 
-type user struct {
-	repository
-}
+type user struct{}
 
-func UserRepository(client database.QueryExecutor) domain.UserRepository {
-	return &user{
-		repository: repository{
-			client: client,
-		},
-	}
+func UserRepository() domain.UserRepository {
+	return new(user)
 }
 
 var _ domain.UserRepository = (*user)(nil)
@@ -31,17 +25,17 @@ var _ domain.UserRepository = (*user)(nil)
 // -------------------------------------------------------------
 
 // Human implements [domain.UserRepository].
-func (u *user) Human() domain.HumanRepository {
+func (u user) Human() domain.HumanRepository {
 	return &userHuman{user: u}
 }
 
 // Machine implements [domain.UserRepository].
-func (u *user) Machine() domain.MachineRepository {
+func (u user) Machine() domain.MachineRepository {
 	return &userMachine{user: u}
 }
 
 // List implements [domain.UserRepository].
-func (u *user) List(ctx context.Context, opts ...database.QueryOption) (users []*domain.User, err error) {
+func (u user) List(ctx context.Context, client database.QueryExecutor, opts ...database.QueryOption) (users []*domain.User, err error) {
 	options := new(database.QueryOpts)
 	for _, opt := range opts {
 		opt(options)
@@ -54,7 +48,7 @@ func (u *user) List(ctx context.Context, opts ...database.QueryOption) (users []
 	options.WriteLimit(&builder)
 	options.WriteOffset(&builder)
 
-	rows, err := u.client.Query(ctx, builder.String(), builder.Args()...)
+	rows, err := client.Query(ctx, builder.String(), builder.Args()...)
 	if err != nil {
 		return nil, err
 	}
@@ -79,7 +73,7 @@ func (u *user) List(ctx context.Context, opts ...database.QueryOption) (users []
 }
 
 // Get implements [domain.UserRepository].
-func (u *user) Get(ctx context.Context, opts ...database.QueryOption) (*domain.User, error) {
+func (u user) Get(ctx context.Context, client database.QueryExecutor, opts ...database.QueryOption) (*domain.User, error) {
 	options := new(database.QueryOpts)
 	for _, opt := range opts {
 		opt(options)
@@ -92,7 +86,7 @@ func (u *user) Get(ctx context.Context, opts ...database.QueryOption) (*domain.U
 	options.WriteLimit(&builder)
 	options.WriteOffset(&builder)
 
-	return scanUser(u.client.QueryRow(ctx, builder.String(), builder.Args()...))
+	return scanUser(client.QueryRow(ctx, builder.String(), builder.Args()...))
 }
 
 const (
@@ -105,7 +99,7 @@ const (
 )
 
 // Create implements [domain.UserRepository].
-func (u *user) Create(ctx context.Context, user *domain.User) error {
+func (u user) Create(ctx context.Context, client database.QueryExecutor, user *domain.User) error {
 	builder := database.StatementBuilder{}
 	builder.AppendArgs(user.InstanceID, user.OrgID, user.ID, user.Username, user.Traits.Type())
 	switch trait := user.Traits.(type) {
@@ -116,15 +110,15 @@ func (u *user) Create(ctx context.Context, user *domain.User) error {
 		builder.WriteString(createMachineStmt)
 		builder.AppendArgs(trait.Description)
 	}
-	return u.client.QueryRow(ctx, builder.String(), builder.Args()...).Scan(&user.CreatedAt, &user.UpdatedAt)
+	return client.QueryRow(ctx, builder.String(), builder.Args()...).Scan(&user.CreatedAt, &user.UpdatedAt)
 }
 
 // Delete implements [domain.UserRepository].
-func (u *user) Delete(ctx context.Context, condition database.Condition) error {
+func (u user) Delete(ctx context.Context, client database.QueryExecutor, condition database.Condition) error {
 	builder := database.StatementBuilder{}
 	builder.WriteString("DELETE FROM users")
 	writeCondition(&builder, condition)
-	_, err := u.client.Exec(ctx, builder.String(), builder.Args()...)
+	_, err := client.Exec(ctx, builder.String(), builder.Args()...)
 	return err
 }