Set up alembic migration usage (#954)

* Set up alembic migration usage

* Fix import order, add isort as alembic hook

* Only run migrations if needed

* Include date as part of migration file name for better sorting

* Skip initial migrations if tables already exist
This eases the transition from a pre-alembic state

* Fix deprecation warning in alembic revision

* Add alembic test stubs

alembic/env.py

@@ -0,0 +1,77 @@
+from sqlalchemy import engine_from_config, pool
+
+import mealie.db.models._all_models  # noqa: F401
+from alembic import context
+from mealie.core.config import get_app_settings
+from mealie.db.models._model_base import SqlAlchemyBase
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+target_metadata = SqlAlchemyBase.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+# Set DB url from config
+settings = get_app_settings()
+config.set_main_option("sqlalchemy.url", settings.DB_URL)
+
+
+def run_migrations_offline():
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online():
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection, target_metadata=target_metadata, user_module_prefix="mealie.db.migration_types."
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()