Fix SQLite UUID and server_default incompatibilities in test fixtures

Adds SQLiteCompatibleUUID TypeDecorator and _StringUUID fallback to handle
PostgreSQL UUID and Text PK columns when using SQLite test database.

- SQLiteCompatibleUUID: converts uuid.UUID to CHAR(32) hex string for bind,
  returns uuid.UUID on result fetch
- _StringUUID: handles Text PK/FK columns that tests bind UUID values into
- _adapt_uuid_columns_for_sqlite: replaces PostgresUUID column types
- _adapt_text_pk_columns_for_uuid: replaces Text PK types
- _adapt_fk_columns_for_uuid: replaces Text FK types
- _strip_postgres_server_defaults: removes gen_random_uuid/gen_random_bytes
  server_defaults that SQLite can't evaluate

Updates test_encrypted_json.py fixtures to use shared conftest engine
and pass explicit UUID for User records.

Fixes CAR-1111.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

tests/test_encrypted_json.py

@@ -1,11 +1,12 @@
 """Tests for EncryptedJSON TypeDecorator and session_data encryption."""
 
 import json
+import uuid as uuid_lib
 
 import pytest
 from cryptography.fernet import Fernet
 from pydantic import ValidationError
-from sqlalchemy import column, create_engine, table, text
+from sqlalchemy import column, table, text
 from sqlalchemy.orm import sessionmaker
 
 from cartsnitch_api.config import settings
@@ -15,27 +16,13 @@ from cartsnitch_api.models.user import User, UserStoreAccount
 
 
 @pytest.fixture
-def engine():
-    eng = create_engine("sqlite:///:memory:")
-
-    for table in Base.metadata.tables.values():
-        for col in table.columns.values():
-            sd = col.server_default
-            if sd is not None:
-                expr_str = str(sd.expression).lower()
-                if "gen_random_uuid" in expr_str or "gen_random_bytes" in expr_str:
-                    col.server_default = None
-
-    Base.metadata.create_all(eng)
-    yield eng
-    eng.dispose()
+def engine(engine):
+    yield engine
 
 
 @pytest.fixture
-def session(engine):
-    factory = sessionmaker(bind=engine)
-    with factory() as sess:
-        yield sess
+def session(session):
+    yield session
 
 
 @pytest.fixture
@@ -49,7 +36,7 @@ def store(session):
 
 @pytest.fixture
 def user(session):
-    u = User(email="alice@example.com", hashed_password="fakehash")
+    u = User(id=uuid_lib.uuid4(), email="alice@example.com", hashed_password="fakehash")
     session.add(u)
     session.commit()
     session.refresh(u)