[FS-672] Improve swagger docs for Client fields.

[stephen-smith]

FS-672

Checklist

• The PR Title explains the impact of the change.
• The PR description provides context as to why the change should occur and what the code contributes to that effect. This could also be a link to a JIRA ticket or a Github issue, if there is one.
• I updated changelog.d subsections with one or more entries.

[pcapriotti]

It would be good to also improve the example. Right now it reads:

    "mls_public_keys": {
      "additionalProp1": "string",
      "additionalProp2": "string",
      "additionalProp3": "string"
    },

which is not very useful.

[fisx]

when building this, running http://localhost:8080/swagger-ui/, and opening http://localhost:8080/swagger-ui/, I see this:

MLSPublicKeys shouldn't be empty, should it?

[stephen-smith]

MLSPublicKeys shouldn't be empty, should it?

It doesn't have any fields, so yes, I think it is supposed to be empty in that display.

As best as I can tell, that's normal for map/dict types in swagger.

The example should have the only valid key and an example value, and there should also be a description if you expand the name.

[pcapriotti]

LGTM