Return 204 on /ack success instead of JSON true

[letmaik]

Addresses first point of #1944.

[achamayou]

@letmaik thank you, that looks good. Since this is a REST API change, would you mind adding an entry to CHANGELOG.md?

We could use https://github.com/openapi-tools/open-api-diff, the markdown diff looks quite reasonable, and may even be generated automatically on release.

[letmaik]

@letmaik thank you, that looks good. Since this is a REST API change, would you mind adding an entry to CHANGELOG.md?

Will do, I always forget.

I just realized that CCF only supports 200 when using set_auto_schema. Any suggestions on how to extend that?

[achamayou]

Pinging @eddyashton, I think it's just a matter of adding a default argument to set_auto_schema() and using it line 337?

[eddyashton]

Yes - what @achamayou said should be sufficient.

[ghost]

letmaik/ack-204@17695 aka 20210118.29 vs master ewma over 50 builds from 17034 to 17692

[letmaik]

@achamayou @eddyashton I had to do a bit more plumbing but I think I ended up at something good. If set_auto_schema is called with a void response schema then it defaults to 204 now.

[achamayou]

@letmaik that does seem like a sensible default, but we may still want to support user-defined 2xx, like Created etc in the future. Agree it's out of scope for this change though.

[letmaik]

@letmaik that does seem like a sensible default, but we may still want to support user-defined 2xx, like Created etc in the future. Agree it's out of scope for this change though.

This PR allows specifiying a custom status code. Isn't that what you mean?