DLTP-213 Reworking on function to write fedora message to custom channel

DLTP-189  Replace blue warning edit button to orange warning resolve button empty file

Adding function to write message to  custom channel

Adding rspec-given to curate gemspec and to generator
Log exception that occured on attaching files
Spec to test the new config method

Fixing the incorrect method call to deliver_fedora_integrity_message

Renaming deliver_fedora_integrity_message to fedora_integrity_message_delivery

Extracting engine default behaviour to private method in engine configuration