feat!: Deprecate SSEServerInfo base_url in favour of url

[vblagoje]

Why

This PR deprecates the base_url parameter in favor of a single url argument for configuring the SSE client. It adds deprecation warnings and updates relevant classes to reflect this change.

This change aligns with common usage patterns—users are typically more familiar with providing the full URL including the /sse endpoint, and omitting it (via base_url) can be unintuitive or error-prone. Simplifying the interface improves clarity and consistency.

Details

• Adds a deprecation warning if base_url is used.
• Ensures that only one of url or base_url can be passed.
• Updates both SSEClient and SSEServerInfo to enforce and reflect this change.

Deprecation Notice

base_url is now deprecated and will be removed in a future release. Please switch to using the full url (including the /sse path) when initializing the client.

Checklist

• Backward compatibility maintained (with warning)
• Clear error handling for conflicting or missing parameters
• Docstrings and inline comments updated

[vblagoje]

@anakin87 @mpangrazzi is already familiar with this discussion - it is a small change that will improve devX as users are mostly used to providing MCP server URL with /sse suffix rather than just base_url and intuitively seem more future proof.

[vblagoje]

cc @bilgeyucel this is the devX upgrade we talked about

[vblagoje]

@anakin87 @mpangrazzi can you please take another look now? There are some minor internal simplifications that are not public and make everything much simpler

[anakin87]

I am ignoring this PR because I thought that Michele had more context. In case it is urgent, please let me know.

[vblagoje]

@anakin87 np, @mpangrazzi has all the context and @oryx1729 can also chime in with his UI/UX experience around this matter

[mpangrazzi]

LGTM! - I've left only a minor comment