fix: implicit invitation to specific service

[genaris]

It seems that our implicit invitation implementation for DID Exchange does not conform exactly with what's written in RFC 0023:

An invitation is presented in one of two forms:

An explicit out-of-band invitation with its own @id.
An implicit invitation contained in a DID document's service attribute that conforms to the DIDComm conventions.
When a request responds to an explicit invitation, its ~thread.pthid MUST be equal to the @id property of the invitation as described in the out-of-band RFC.

When a request responds to an implicit invitation, its ~thread.pthid MUST contain a DID URL that resolves to the specific service on a DID document that contains the invitation.

So it assumes that the implicit invitation should go to a specific service that contains a suitable DIDComm communication endpoint (e.g. did:method:example#invitation). However, in our implementation we are simply using the did and just selecting the highest priority DIDComm service.

Whilst I don't think it is bad for implicit invitations to work the way we are using it, here I'm adding the possibility of directing them to a specific service, so it will use it instead of resolving all DIDComm services the DID Document may have.

[codecov-commenter]

Codecov Report

Merging #1592 (1b78bf1) into main (dd75be8) will increase coverage by 4.27%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1592      +/-   ##
==========================================
+ Coverage   81.46%   85.73%   +4.27%     
==========================================
  Files         950      950              
  Lines       22838    22842       +4     
  Branches     4010     4013       +3     
==========================================
+ Hits        18604    19584     +980     
+ Misses       3959     3073     -886     
+ Partials      275      185      -90     

Files	Coverage Δ
...src/modules/connections/ConnectionsModuleConfig.ts	77.77% <ø> (ø)
.../modules/connections/services/ConnectionService.ts	86.49% <100.00%> (+0.04%)	⬆️
...modules/didcomm/services/DidCommDocumentService.ts	100.00% <100.00%> (ø)
packages/core/src/modules/oob/OutOfBandApi.ts	90.47% <100.00%> (ø)

... and 31 files with indirect coverage changes