There was really no reason to go with "Messages" as far as the
vocabulary of the Groupware API goes, since the objects those APIs serve
are "Emails", to stick with the wording of the JMAP specification.
* refactor some pkg/jmap and groupware methods to make more sense from
an API point-of-view
* add path parameter documentation, but automate it by injecting their
definition into the OpenAPI YAML tree that is extracted from the
source code using go-swagger as it is too cumbersome, repetitive and
error-prine to document them in the source code; wrote a TypeScript
file apidoc-process.ts to do so
* add generating an offline HTML file for the OpenAPI documentation
using redocly, and injecting a favicon into the resulting HTML; wrote
a TypeScript file apidoc-postprocess-html.ts to do so