Providing a type that isn't mapped in connectContentTypeMap sends empty appMode

[dotNomad]

As we learned in #2476 (comment) when providing a type in the Configuration file that isn't in connectContentTypeMap the manifest sent to Connect provides "" (as it is the UnknownMode).

In an effort to better support Publisher working when Connect updates without code changes the appMode should be sent using the provided type string in the Configuration file rather than falling back to "" if it is unrecognized.

Reference:

publisher/internal/clients/connect/apptypes.go

Line 258 in 0b43655

var connectContentTypeMap = map[config.ContentType]AppMode{