Implement Gitea GPG API #14
Description
as implemented by: go-gitea/go-sdk#36 which follows the github specification.
GoGs may or may not get it done one day (cf gogs/gogs#2321).
Here's the go-sdk implementation: https://github.com/go-gitea/go-sdk/blob/master/gitea/user_gpgkey.go