feat: api to add new loc scheme

[iFergal]

This allows us to add new location/URL entries for endpoint identifiers that have a role.

I'll be using it to allow an issuer to add a schema discovery endpoint using the new indexer role - WebOfTrust/keripy#920 - with itself as the eid. So the URL can be retrieved via the base OOBI http://keria.com/{controllerPre}. (not .../agent/{agentPre})

This can be extended to have a proper way to retrieve the endpoint given the OOBI, but for my purposes right now it's OK to just parse the OOBI GET response because it's just for fetching SAIDs.

[codecov]

Codecov Report

Attention: Patch coverage is 98.31933% with 2 lines in your changes missing coverage. Please review.

Project coverage is 93.77%. Comparing base (ab20766) to head (4d6b361).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/keria/app/aiding.py	96.66%	1 Missing ⚠️
src/keria/core/longrunning.py	91.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #352      +/-   ##
==========================================
+ Coverage   93.71%   93.77%   +0.06%     
==========================================
  Files          37       37              
  Lines        8293     8407     +114     
==========================================
+ Hits         7772     7884     +112     
- Misses        521      523       +2     

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[2byrds]

Lgtm