allow to extend transport implementation to provide additional sessio…

[mswiderski]

…n handling

change visibility of transport implementations constructor

Motivation and Context

To be able to extend transports (in our case to provide additional handling of sessions) having private constructors make it no-go.

How Has This Been Tested?

Custom extension to transport are implemented and tested with MCP client

Breaking Changes

No

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context