Provide a way for middleware to get the error from a tool call,
demonstrating that we can add this functionality without making a
breaking change.
Leave getError unexported for now; we can export it (and setError) at
any time.
For #64.
Change the design of tool handlers by removing genericity from the common path.
- `ToolHandler` gets the args as a `json.RawMessage`. Using Server.AddTool does no unmarshaling or schema validation.
- `ToolHandlerFor`, installed with `AddTool`, are the only generic pieces.
TODO:
uncomment and fix some tests
Introduces a new test file content_nil_test.go which verifies that UnmarshalJSON methods for various Content types do not panic when unmarshaling onto nil pointers.
Adds a nil check in contentFromWire function to guard against a nil wire.Content parameter.
Tests cover different scenarios, including valid and invalid content types, as well as cases with empty or missing content fields.
For #205
