[Feat]: Support additional AgentCard discovery mechanism

[bernardoVale]

Is your feature request related to a problem? Please describe.

Currently, A2AClient is coupled with the well-known URI discovery mechanisms, preventing consumers from discovering agent cards using a different method.

Describe the solution you'd like

Ideally, the SDK should adopt a flexible approach, similar to the Python SDK where A2AClient accepts a static card so that consumers of the SDK can discovery agent card using different methods and instantiate a client with the card

Describe alternatives you've considered

No response

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[mprynce]

I submitted a PR #33 that fixes the .well-known requirement and allows agents at other paths such as /agents/coder to have their agent card at /agents/coder/agent.json. I believe there will be many registries of agents and simply having a unique URL for each agent card is sufficient for all the registries to operate.

I have another PR in the a2a-samples that demonstrates a single server with multiple agent cards: a2aproject/a2a-samples#163

[bernardoVale]

@mprynce that's great, but with #33 A2AClient is still responsible for fetching a card. You can't instantiate an A2AClient with an existing card.

[mprynce]

@mprynce that's great, but with #33 A2AClient is still responsible for fetching a card. You can't instantiate an A2AClient with an existing card.

Sorry, I missed that point in your original request.

I always like an "options" parameter that can provide overrides, for things like fetch(). My #33 PR also includes an options parameter and it could be very easy to add an options.agentCard that can override the fetch by the client

[swapydapy]

Resolved in #121