## Introduce Configuration class for StreamableHttpServerTransport
Replace the six-parameter flat constructor of
`StreamableHttpServerTransport` with a typed `Configuration` class. This
improves API ergonomics, enables structural equality and copy(), and
provides a stable extension point for future options without further
breaking the constructor signature.
### Changes:
- Add `Configuration` as a public class nested directly on
`StreamableHttpServerTransport`, with `enableJsonResponse` as the first
parameter (most commonly set)
- Change the primary constructor to accept `Configuration`.
- Rename `retryIntervalMillis: Long?` to `retryInterval: Duration?` in
Configuration, aligning with Kotlin's type-safe time API
- Deprecate the old flat constructor with a compatibility bridge
- Update KotlinTestBase integration test to use the new constructor
- Enable test
AbstractResourceIntegrationTest.testSubscribeAndUnsubscribe() since #249
is closed
## Motivation and Context
The current StreamableHttpServerTransport API cannot be easily extended:
adding more parameters would be a breaking change. But this is already
needed for #521.
This PR is a prerequisite for #535
## How Has This Been Tested?
Regression tests
## Breaking Changes
No. Current StreamableHttpServerTransport constructor was deprecated
## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed
ec53adc317