Create access module package

src/govoplan_access/backend/tenancy/__init__.py

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+"""Tenant datastore routing abstractions."""
+

src/govoplan_access/backend/tenancy/datastore.py

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+from __future__ import annotations
+
+from collections.abc import Generator
+from contextlib import contextmanager
+from dataclasses import dataclass
+from typing import Literal, Protocol
+
+from sqlalchemy.orm import Session, sessionmaker
+
+
+DatastoreMode = Literal["shared", "schema", "database"]
+
+
+@dataclass(frozen=True, slots=True)
+class TenantDatastoreRef:
+    tenant_id: str
+    mode: DatastoreMode = "shared"
+    datastore_id: str | None = None
+    schema_name: str | None = None
+    database_url_secret_ref: str | None = None
+
+
+class TenantDatastore(Protocol):
+    ref: TenantDatastoreRef
+
+    @contextmanager
+    def session_for(self, module_id: str) -> Generator[Session, None, None]:
+        ...
+
+
+class DatastoreResolver(Protocol):
+    def for_tenant(self, tenant_id: str) -> TenantDatastore:
+        ...
+
+
+class SharedTenantDatastore:
+    def __init__(self, ref: TenantDatastoreRef, session_factory: sessionmaker[Session]) -> None:
+        self.ref = ref
+        self._session_factory = session_factory
+
+    @contextmanager
+    def session_for(self, module_id: str) -> Generator[Session, None, None]:
+        del module_id
+        with self._session_factory() as session:
+            yield session
+
+
+class SharedDatastoreResolver:
+    def __init__(self, session_factory: sessionmaker[Session]) -> None:
+        self._session_factory = session_factory
+
+    def for_tenant(self, tenant_id: str) -> TenantDatastore:
+        return SharedTenantDatastore(TenantDatastoreRef(tenant_id=tenant_id), self._session_factory)
+