feat: Added support for sending messages through simple HTTP-based transports

[awoie]

Potentially closes #552 and potentially closes #469

Contains:

• Added transport interfaces to be used with DIDComm module.
• Added simple implementation of an HTTP-based transport
• Implemented sending DIDComm messages

Add a list of supported transports to the DIDComm plugin:

new DIDComm([new DIDCommHttpTransport()])

Then, use the DIDComm module to send messages to a DID:

const message = {
  type: 'test',
  to: receiver.did,
  from: sender.did,
  id: 'test',
  body: { hello: 'world' },
}
const packedMessage = await agent.packDIDCommMessage({
  packing: 'authcrypt',
  message,
})
const result = await agent.sendDIDCommMessage({
  messageId: '123',
  packedMessage,
  recipientDidUrl: receiver.did
})

[codecov]

Codecov Report

Merging #610 (844baab) into next (0bf7b24) will increase coverage by 10.33%.
The diff coverage is 92.45%.

@@             Coverage Diff             @@
##             next     #610       +/-   ##
===========================================
+ Coverage   67.58%   77.91%   +10.33%     
===========================================
  Files          62       78       +16     
  Lines        1530     2318      +788     
  Branches      247      415      +168     
===========================================
+ Hits         1034     1806      +772     
- Misses        400      510      +110     
+ Partials       96        2       -94     

[mirceanis]

looks great