feat(dir): add DID Auth support

[DaevMithran]

Adds DID-based authentication alongside existing SPIFFE/SPIRE modes for decentralized identity networks.

Changes

New Authentication Mode

• Added did auth mode in server and client (alongside jwt and x509)
• Uses Universal Resolver HTTP API for DID resolution
• Supports did:cheqd and other W3C DID methods

[ramizpolic]

Hi @DaevMithran, thank you for your contribution! Although this is LGTM from my end, I do want to ask for some supporting material, either as part of documentation or some simple guide in terms of:

• How can we use DIDs for network setup -- with SPIFFE, we have a way to configure networks through federation (dir-staging repo as an entrypoint), are there similar methods for DIDs?
• How are we going to control the authorization rules? Although currently the authz rules are static and we are moving these to be dynamically managed, the question is: what should be the policy when using DIDs -- e.g. DID-A can do OP-A and OP-B.
• How are we going to (and should we at all) support the cases of nodes sharing different authentication methods -- Node A working in DID mode and Node B in SPIFFE mode? If no node-to-node communication is allowed, then this can be handled on a network where a network has a common auth mode.
• Is there a way we can access additional material beyond verification from the resolver node?

Although the current PR only supports JS clients to make use of DIDs, I think it is okay to support other clients (go/python/cli) later on.

Regarding the PR itself, we may want to cover this with at least one test case that would help us maintainers understand the setup. In that regard, having a script/document/rfc/testcase that at least showcases the usage of DID would be extremely helpful. If you have a working approach to utilising DIDs at the moment, that would also be very beneficial.