Fix special character password support in alembic (#811)

Author: MortyZhaoy

backend/alembic/env.py

@@ -39,7 +39,9 @@
 target_metadata = MappedBase.metadata
 
 # other values from the config, defined by the needs of env.py,
-alembic_config.set_main_option('sqlalchemy.url', SQLALCHEMY_DATABASE_URL.render_as_string(hide_password=False))
+alembic_config.set_main_option(
+    'sqlalchemy.url', SQLALCHEMY_DATABASE_URL.render_as_string(hide_password=False).replace('%', '%%')
+)
 
 
 def run_migrations_offline():