feat(backend): state persisted objects (#9870)

This PR initiates the rework of Zitadel's backend to state-persisted
objects. This change is a step towards a more scalable and maintainable
architecture.

## Changes

* **New `/backend/v3` package**: A new package structure has been
introduced to house the reworked backend logic. This includes:
* `domain`: Contains the core business logic, commands, and repository
interfaces.
* `storage`: Implements the repository interfaces for database
interactions with new transactional tables.
  * `telemetry`: Provides logging and tracing capabilities.
* **Transactional Tables**: New database tables have been defined for
`instances`, `instance_domains`, `organizations`, and `org_domains`.
* **Projections**: New projections have been created to populate the new
relational tables from the existing event store, ensuring data
consistency during the migration.
* **Repositories**: New repositories provide an abstraction layer for
accessing and manipulating the data in the new tables.
* **Setup**: A new setup step for `TransactionalTables` has been added
to manage the database migrations for the new tables.

This PR lays the foundation for future work to fully transition to
state-persisted objects for these components, which will improve
performance and simplify data access patterns.

This PR initiates the rework of ZITADEL's backend to state-persisted
objects. This is a foundational step towards a new architecture that
will improve performance and maintainability.

The following objects are migrated from event-sourced aggregates to
state-persisted objects:

* Instances
  * incl. Domains
* Orgs
  * incl. Domains

The structure of the new backend implementation follows the software
architecture defined in this [wiki
page](https://github.com/zitadel/zitadel/wiki/Software-Architecturel).

This PR includes:

* The initial implementation of the new transactional repositories for
the objects listed above.
* Projections to populate the new relational tables from the existing
event store.
* Adjustments to the build and test process to accommodate the new
backend structure.

This is a work in progress and further changes will be made to complete
the migration.

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Iraq Jaber <iraq+github@zitadel.com>
Co-authored-by: Iraq <66622793+kkrime@users.noreply.github.com>
Co-authored-by: Tim Möhlmann <tim+github@zitadel.com>

backend/v3/domain/instance_domain.go

@@ -0,0 +1,79 @@
+package domain
+
+import (
+	"context"
+	"time"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+)
+
+type InstanceDomain struct {
+	InstanceID string `json:"instanceId,omitempty" db:"instance_id"`
+	Domain     string `json:"domain,omitempty" db:"domain"`
+	// IsPrimary indicates if the domain is the primary domain of the instance.
+	// It is only set for custom domains.
+	IsPrimary *bool `json:"isPrimary,omitempty" db:"is_primary"`
+	// IsGenerated indicates if the domain is a generated domain.
+	// It is only set for custom domains.
+	IsGenerated *bool      `json:"isGenerated,omitempty" db:"is_generated"`
+	Type        DomainType `json:"type,omitempty" db:"type"`
+
+	CreatedAt time.Time `json:"createdAt,omitzero" db:"created_at"`
+	UpdatedAt time.Time `json:"updatedAt,omitzero" db:"updated_at"`
+}
+
+type AddInstanceDomain struct {
+	InstanceID  string     `json:"instanceId,omitempty" db:"instance_id"`
+	Domain      string     `json:"domain,omitempty" db:"domain"`
+	IsPrimary   *bool      `json:"isPrimary,omitempty" db:"is_primary"`
+	IsGenerated *bool      `json:"isGenerated,omitempty" db:"is_generated"`
+	Type        DomainType `json:"type,omitempty" db:"type"`
+
+	// CreatedAt is the time when the domain was added.
+	// It is set by the repository and should not be set by the caller.
+	CreatedAt time.Time `json:"createdAt,omitzero" db:"created_at"`
+	// UpdatedAt is the time when the domain was last updated.
+	// It is set by the repository and should not be set by the caller.
+	UpdatedAt time.Time `json:"updatedAt,omitzero" db:"updated_at"`
+}
+
+type instanceDomainColumns interface {
+	domainColumns
+	// IsGeneratedColumn returns the column for the is generated field.
+	IsGeneratedColumn() database.Column
+	// TypeColumn returns the column for the type field.
+	TypeColumn() database.Column
+}
+
+type instanceDomainConditions interface {
+	domainConditions
+	// TypeCondition returns a filter for the type field.
+	TypeCondition(typ DomainType) database.Condition
+}
+
+type instanceDomainChanges interface {
+	domainChanges
+	// SetType sets the type column.
+	SetType(typ DomainType) database.Change
+}
+
+type InstanceDomainRepository interface {
+	instanceDomainColumns
+	instanceDomainConditions
+	instanceDomainChanges
+
+	// Get returns a single domain based on the criteria.
+	// If no domain is found, it returns an error of type [database.ErrNotFound].
+	// If multiple domains are found, it returns an error of type [database.ErrMultipleRows].
+	Get(ctx context.Context, opts ...database.QueryOption) (*InstanceDomain, error)
+	// List returns a list of domains based on the criteria.
+	// If no domains are found, it returns an empty slice.
+	List(ctx context.Context, opts ...database.QueryOption) ([]*InstanceDomain, error)
+
+	// Add adds a new domain to the instance.
+	Add(ctx context.Context, domain *AddInstanceDomain) error
+	// Update updates an existing domain in the instance.
+	Update(ctx context.Context, condition database.Condition, changes ...database.Change) (int64, error)
+	// Remove removes a domain from the instance.
+	Remove(ctx context.Context, condition database.Condition) (int64, error)
+}