fix(Fastify session ts): wrong request session injected into the handler function

[kriskw1999]

Summary of change

Fix Type Mismatch in verifySession Function for Fastify Routes

Description:

sandbox:

• Here you can find a codesandbox with the issue
• NOTE: take a look at the error of Typescript in console, don't worry about the lint on the code it is an issue with code sandbox
• https://codesandbox.io/p/devbox/fastify-typescript-forked-k38hsl?file=%2Findex.ts%3A42%2C4

Issue:

• The verifySession function in the Fastify application incorrectly uses the SuperTokens' SessionRequest type, leading to a type mismatch.
• When using Fastify's get method, the expected dynamic request type from the handler function was being overshadowed by the SuperTokens type.

Solution:

• Proposed a more flexible approach by introducing a new generic to the verifySession function.
• Modified the verifySession function to accept a generic type parameter T, extending from Fastify's OriginalFastifyRequest.

Technical Details:

• Original Code:

  // Problematic implementation
  export declare function verifySession(
    options?: VerifySessionOptions
  ): (req: SessionRequest, res: FastifyReply) => Promise<void>;

• Proposed Solution:

  // Revised implementation with generic type
  export declare function verifySession<T extends OriginalFastifyRequest>(
    options?: VerifySessionOptions
  ): (req: SessionRequest<T>, res: FastifyReply) => Promise<void>;

Impact:

• Ensures correct type inference for Fastify route handlers using verifySession.
• Enhances type safety and compatibility with Fastify's dynamic type resolution mechanism.
• It should not change any existing code because just decorates the new type with a generic providing a default value to it

Additional Notes:

• please note that you cannot add this generic without changing the interface into the type because it shows an error of potentially wrong interface implementation.
• please note this is just a proposal to fix these kind of issues, feel free to propose an alternative solution!

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[porcellus]

The code change looks good to me. Before merging, we'd need:

• Some note added into the changelog
• Increased patch version (see the original PR template)

I'm happy to take over as well if you don't want to do those parts.

[kriskw1999]

@porcellus ok now I guess that I have done all the stuff. If I missed something let me know!