Allows for new issuing credential library implementations in the future.
Moved db and decrypt logic to privateCredentialLibraryAllTypes from
issueCredentialLibrary.
This also removes sessionId from retrieveCredential, it was not needed
and removing allows retrieveCredential to be reused for credentials
issued outside current workflow.
* add custom ResponseWriter struct to inject custom response headers based on status code
* docs
* upgrade listenerutil
* fix config tests
* replace all instances of "data:*" with "data:" to reflect changes to listenerutil
* swapping strings.HasPrefix in favor of mux.Handler for ui request matching
* set ui path as const
* add custom response headers to changelog
Danielle