Automate update of openapi-clients

[jennydaman]

Feature request: use GitHub Actions to automatically update https://github.com/FNNDSC/openapi-clients

• create a GitHub Actions which triggers on release
• It downloads schema_split.yaml from the current and previous release, comparing them using openapi-diff.
• If state is either compatible or incompatible, clone https://github.com/FNNDSC/openapi-clients and...
  • increase the value of version.txt according to semantic versioning (minor version increase for compatible, major version increase for incompatible)
  • regenerate all client code
  • create a PR to main branch