Support DID and verifier attesation schemes

[babisRoutis]

This PR adds support for two additional client_id_scheme(s)

• did
• verifier_attestation

DID

To be used wallet needs to add to its configuration an instance of SupportedClientIdScheme.DID.
Effectually, to do so, it has to provide a way to lookup verifier's public key using a DID URL via DID resolution.
The later is out of scope of the library

Verifier Attestation

To be used wallet needs to add to its configuration an instance of SupportedClientIdScheme.VerifierAttestation.
To do so, wallet has to provide a JWSVerifier capable of verifying the signature of verifier attestation JWT from trusted issuers.

Closes #244
Closes #126

[dzarras]

@babisRoutis java.net.URI is not the best option to parse DIDs/DIDURLs. For instance check here how Example 6 did:example:123?service=agent&relativeRef=/credentials#degree from did-core is parsed.