fix: always use Agent proxy when sending messages from SignifyGroupHab

[kentbull]

This fixes delegated multisig rotation with KERIA and Signify multisig groups. Prior to this fix then sending a delegated multisig rotation would always trigger a kering.KeriError as shown below because the existing if else chain sets `phab = hab as shown below.

First, the def sign in SignifyHab throwing the KeriError.

class SignifyHab(BaseHab):
    ...
    def sign(self, ser, verfers=None, indexed=True, indices=None, ondices=None, **kwa):
        ...
        raise kering.KeriError("Signify hab does not support local signing")

Next, the if/else chain in keria.app.delegating.Anchorer.processPartialWitnessEscrow

class Anchorer:
    ...
    def processPartialWitnessEscrow(...):
        ...
                if isinstance(hab, habbing.GroupHab):
                    phab = hab.mhab
                elif hab.kever.sn > 0:
                    phab = hab  # <-- this branch was being incorrectly called because for SignifyGroupHab instances where the delegate has undergone a rotation result in this branch evaluating to true, preventing the check for the self.proxy.
                elif self.proxy is not None:
                    phab = self.proxy
        ...

The new code causes this Anchorer to always check for a proxy and use it if specified:

                if isinstance(hab, habbing.GroupHab):
                    phab = hab.mhab
                elif self.proxy is not None:
                    phab = self.proxy
                elif hab.kever.sn > 0:
                    phab = hab

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 93.78%. Comparing base (ab20766) to head (9e48c70).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/keria/app/delegating.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #353      +/-   ##
==========================================
+ Coverage   93.71%   93.78%   +0.06%     
==========================================
  Files          37       37              
  Lines        8293     8415     +122     
==========================================
+ Hits         7772     7892     +120     
- Misses        521      523       +2     

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[kentbull]

Hey all, can we relax the code coverage for this patch since we don't yet have any signify tests in this repo? I will add a test to the SignifyPy and SignifyTS repo for this later next week or so. I have a Bash script integration test in GLEIF-IT/qvi-software as a start.

[kentbull]

I checked with Phil just now and he said moving these logic branches around are okay because you can always use the proxy when present except when there is a GroupHab.

[2byrds]

We reviewed this in the vLEI dev community meeting. Kent explained the discussions he had with Phil. And this seems to be an appropriate workaround. There is a desire for better tests for these kind of changes. And some of the signifypy related tests would help here.