Submit template name for wcce/wes_cahandler as part of user-agent field

[grindsa]

if you dont mind to let the client specify the template to be used we could re-use the header_info_field feature. There are some other handlers already using the features and the adaption should not be difficult.

Originally posted by @grindsa in https://github.com/grindsa/acme2certifier/discussions/142#discussioncomment-8746988