Generate Swagger in CI and Validate It

[adeutscher]

The standard CI could do with a bit of extra checks around swagger.

Action items:

• Before running solution build, take a checksum of the committed swagger.json and confirm that building the solution didn't change it. If I had a nickel for every time I forgot to do a local build to update Swagger, then I'd have several nickels.

[adeutscher]

This issue was based on an LLM suggestion. I agree with the general sentiment around wanting a bit more checking on Swagger, content but I think that part of the suggestion was not appropriate for this location-agnostic template project. For posterity, the parts of the suggestion that I will not be implementing for this issue were:

• Using the openapi-diff command to compare against the default-branch baseline.
  • In theory, this would raise a CI-breaking stink if a breaking change were introduced (e.g. changed path, renamed property, and so on). However, that wouldn't be a good fit for the template because a developer initializing this template would absolutely be making breaking changes. It is a sound idea, and down the road I could make (as part of a separate issue) a directory of minor initialization suggestions on top of the basic steps that I'm already suggesting in the root README.md.