feat(db-postgres): data migration script from mongo to postgres

agenta-backend/agenta_backend/migrations/mongo_to_postgres/README.md

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+```bash
+docker ps 
+docker exec -it {backend-container-id} bash
+cd /app/agenta_backend/migrations/mongo_to_postgres
+python3 migration.py
+```

agenta-backend/agenta_backend/migrations/mongo_to_postgres/db_engine.py

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+import os
+import logging
+from asyncio import current_task
+from typing import AsyncGenerator
+from contextlib import asynccontextmanager
+
+from sqlalchemy.ext.asyncio import (
+    AsyncSession,
+    create_async_engine,
+    async_sessionmaker,
+    async_scoped_session,
+)
+
+from agenta_backend.utils.common import isCloudEE
+
+if isCloudEE():
+    from agenta_backend.commons.observability.models.db import SpanDB
+    from agenta_backend.commons.models.db_models import (
+        APIKeyDB,
+        WorkspaceDB,
+        OrganizationDB,
+        AppDB_ as AppDB,
+        UserDB_ as UserDB,
+        ImageDB_ as ImageDB,
+        TestSetDB_ as TestSetDB,
+        AppVariantDB_ as AppVariantDB,
+        EvaluationDB_ as EvaluationDB,
+        DeploymentDB_ as DeploymentDB,
+        VariantBaseDB_ as VariantBaseDB,
+        AppEnvironmentDB_ as AppEnvironmentDB,
+        AppEnvironmentRevisionDB_ as AppEnvironmentRevisionDB,
+        EvaluatorConfigDB_ as EvaluatorConfigDB,
+        HumanEvaluationDB_ as HumanEvaluationDB,
+        EvaluationScenarioDB_ as EvaluationScenarioDB,
+        HumanEvaluationScenarioDB_ as HumanEvaluationScenarioDB,
+    )
+else:
+    from agenta_backend.models.db_models import (
+        AppDB,
+        UserDB,
+        ImageDB,
+        TestSetDB,
+        EvaluationDB,
+        DeploymentDB,
+        AppVariantDB,
+        VariantBaseDB,
+        AppEnvironmentDB,
+        AppEnvironmentRevisionDB,
+        EvaluatorConfigDB,
+        HumanEvaluationDB,
+        EvaluationScenarioDB,
+        HumanEvaluationScenarioDB,
+    )
+
+from agenta_backend.models.db_models import (
+    TemplateDB,
+    AppVariantRevisionsDB,
+)
+
+models = [
+    AppDB,
+    UserDB,
+    ImageDB,
+    TestSetDB,
+    TemplateDB,
+    AppVariantDB,
+    DeploymentDB,
+    EvaluationDB,
+    VariantBaseDB,
+    AppEnvironmentDB,
+    AppEnvironmentRevisionDB,
+    EvaluatorConfigDB,
+    HumanEvaluationDB,
+    EvaluationScenarioDB,
+    AppVariantRevisionsDB,
+    HumanEvaluationScenarioDB,
+]
+
+if isCloudEE():
+    models.extend([OrganizationDB, WorkspaceDB, APIKeyDB])  # type: ignore
+
+
+# Configure and set logging level
+logger = logging.getLogger(__name__)
+logger.setLevel(logging.INFO)
+
+
+class DBEngine:
+    """
+    Database engine to initialize SQLAlchemy and return the engine based on mode.
+    """
+
+    def __init__(self) -> None:
+        self.mode = os.environ.get("DATABASE_MODE", "v2")
+        self.db_url = f"{os.environ.get('POSTGRES_URI')}"
+        self.engine = create_async_engine(url=self.db_url)
+        self.async_session_maker = async_sessionmaker(
+            bind=self.engine, class_=AsyncSession, expire_on_commit=False
+        )
+        self.async_session = async_scoped_session(
+            session_factory=self.async_session_maker, scopefunc=current_task
+        )
+
+    async def init_db(self):
+        """
+        Initialize the database based on the mode and create all tables.
+        """
+        async with self.engine.begin() as conn:
+            # Drop all existing tables (if needed)
+            # await conn.run_sync(Base.metadata.drop_all)
+            # Create tables
+            for model in models:
+                await conn.run_sync(model.metadata.create_all)
+        logger.info(f"Using {self.mode} database...")
+
+    async def remove_db(self) -> None:
+        """
+        Remove the database based on the mode.
+        """
+        async with self.engine.begin() as conn:
+            for model in models:
+                await conn.run_sync(model.metadata.drop_all)
+
+    @asynccontextmanager
+    async def get_session(self) -> AsyncGenerator[AsyncSession, None]:
+        session = self.async_session()
+        try:
+            yield session
+        except Exception as e:
+            await session.rollback()
+            raise e
+        finally:
+            await session.close()
+
+    async def close(self):
+        """
+        Closes and dispose all the connections using the engine.
+
+        :raises     Exception:  if engine is initialized
+        """
+
+        if self.engine is None:
+            raise Exception("DBEngine is not initialized")
+
+        await self.engine.dispose()
+
+        self.engine = None
+        self.async_session_maker = None
+        self.async_session = None
+
+
+db_engine = DBEngine()