Decouple JWT and LD signing/verifying paths

[decentralgabe]

fixes #194

Notably, this makes all endpoints use JWTs, leaving LD suites to be a bit lonely. LD suite support is possible but not integrated. Still thinking of the best way to include this...

[codecov-commenter]

Codecov Report

Merging #195 (d384d51) into main (3ced400) will increase coverage by 2.42%.
The diff coverage is 56.62%.

@@            Coverage Diff             @@
##             main     #195      +/-   ##
==========================================
+ Coverage   54.82%   57.25%   +2.42%     
==========================================
  Files          31       32       +1     
  Lines        3732     3726       -6     
==========================================
+ Hits         2046     2133      +87     
+ Misses       1310     1236      -74     
+ Partials      376      357      -19     

Impacted Files	Coverage Δ
crypto/jwk.go	0.00% <0.00%> (ø)
did/model.go	100.00% <ø> (+44.12%)	⬆️
crypto/jwt.go	36.75% <36.75%> (ø)
did/pkh.go	77.00% <56.00%> (+2.56%)	⬆️
credential/exchange/request.go	36.92% <62.50%> (+4.46%)	⬆️
did/web.go	78.90% <68.97%> (+19.10%)	⬆️
did/util.go	53.39% <78.57%> (+15.89%)	⬆️
did/key.go	67.27% <81.82%> (+18.91%)	⬆️
credential/signing/jwt.go	32.92% <83.33%> (ø)
cryptosuite/jsonwebkey2020.go	61.87% <90.00%> (+4.93%)	⬆️
... and 11 more

[decentralgabe]

Added #196 to address

[nitro-neal]

Looks great!