Improve REST API documentation and capabilities

According to the documentation the REST API currently only supports retrieving entries of type Credentials: https://docs.devolutions.net/server/web-interface/utilities/api-documentation

In this version of the API, passwords can only be retrieved from entries of the Credentials type.

IT would be great if all credential types could be retrieved using the REST API as in some use cases it's not an option to use powershell.
Furthermore the above quote is not quite true: For example "PasswordList" is a subtype of "Credential" but can also not be retrieved using the REST API. If not all subtypes are retrievable using the API it'd very useful to know which ones are and which ones aren't.