Add sqlalchemy migration in v2 for bp add-mysql-support-for-freezer

Add sqlalchemy migration frame in v2.
The test will be added in another patch.

ref: https://storyboard.openstack.org/#!/story/2004132

Story: #2004132
Task: #27578

Change-Id: Iec8f96a68f9e640b96c578af09fb5e4410536592
Implements: bp add-mysql-support-for-freezer

freezer_api/db/sqlalchemy/migrate_repo/migrate.cfg

@@ -0,0 +1,20 @@
+[db_settings]
+# Used to identify which repository this database is versioned under.
+# You can use the name of your project.
+repository_id=freezer-api
+
+# The name of the database table used to track the schema version.
+# This name shouldn't already be used by your project.
+# If this is changed once a database is under version control, you'll need to
+# change the table name in each database too.
+version_table=migrate_version
+
+# When committing a change script, Migrate will attempt to generate the
+# sql for all supported databases; normally, if one of them fails - probably
+# because you don't have that database installed - it is ignored and the
+# commit continues, perhaps ending successfully.
+# Databases in this list MUST compile successfully during a commit, or the
+# entire commit will fail. List the databases your application will actually
+# be using to ensure your updates to that database work properly.
+# This must be a list; example: ['postgres','sqlite']
+required_dbs=[]

freezer_api/db/sqlalchemy/migrate_repo/versions/001_freezer_api_init.py

@@ -0,0 +1,32 @@
+#   Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from sqlalchemy import MetaData
+
+CLASS_NAME = 'default'
+
+
+def define_tables(meta):
+
+    return []
+
+
+def upgrade(migrate_engine):
+    meta = MetaData()
+    meta.bind = migrate_engine
+
+    # create all tables
+    # Take care on create order for those with FK dependencies
+    tables = define_tables(meta)
+
+    for table in tables:
+        table.create()