[Feat]: Support HTTP+JSON/REST

[alirussell]

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

Im trying to use the client to connect to a server that only supports HTTP+JSON/REST, but the client doesn't seem to support this at all, and defaults to JSON-RPC.

Describe the solution you'd like

The client should detect what transports protocols are supported by the agent card and then use the most appropriate one.

Describe alternatives you've considered

Building my own client directly using the REST endpoints.

Additional context

I am building a more generic client for our platform, which needs to be able to support all transports.

Code of Conduct

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

[micahkatz]

Can this work with the spec to do /rpc for jsonrpc transports for streaming? This is already implement in python sdk

[tchapacan]

I'm planning to open a PR for the client support in the continuation of the server part, commenting here just for visibility and make sure no duplicate work will be done.