Update Cachito API documentation

[serg-cymbaluk]

CLOUDBLD-7666

Fix the documentation mismatches with the actual API.

Maintainers will complete the following section

• Commit messages are descriptive enough
• Code coverage from testing does not decrease and new code is covered
• OpenAPI schema is updated (if applicable)
• DB schema change has corresponding DB migration (if applicable)
• README updated (if worker configuration changed, or if applicable)

[brunoapimentel]

It's more of a nitpick, but I noticed that the lib that creates the API docs crops the titles at 51 chars, no matter the size of the screen:

The last 3 endpoints are all over that limit, which makes them harder to read.

I also noticed that the titles are supposed to be read from a key named summary. Since we're only using description, the info there is copied to both the title and the description of each endpoint.

It seems that the 51 chars limitation is only applied to the title (summary), not to the description, so we could use both keys in case we need more information while describing an endpoint.

[serg-cymbaluk]

@brunoapimentel

Added summaries for endpoints.

[brunoapimentel]

LGTM

[akhmanova]

LGTM