Add Phase A deprecation/migration banner

feat(graphql): SZL GraphQL gateway — LICENSE

feat(graphql): SZL GraphQL gateway — README.md

feat(graphql): SZL GraphQL gateway — Dockerfile

feat(graphql): SZL GraphQL gateway — requirements.txt

feat(graphql): SZL GraphQL gateway — szl_graphql_schema.py

feat(graphql): SZL GraphQL gateway — app.py

initial commit