fix(server): fetch adapter endpoint path with trailing slash causes 404

[maddsua]

Extends PR 4893

This was discussed in private, but just for the reference what is it all about:

Having a trailing slash in endpoint path caused 404's.

Now it doesn't =)

Closes #4893

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[tclain-pillar]

Seems broken still:

with a custom endpoint, this

let path = url.pathname.slice(
    opts.endpoint.length + (opts.endpoint.endsWith("/") ? 0 : 1)
  );

/custom-endpoint/path.to.proc gets resolved to /path.to.proc thus still causing a 404, instead of the expected path.to.proc in the procedure map.

(
We use the hono (very thin wrapper around the fetch adapter) for instance and this broke our production release gloriously (range update on CI :-( ) for a couple of hours.

on hono side, we use trailing url as recommended by hono doc:

 trpcServer({
    router: saasApiRouter,
    createContext: createContextForHono("api-saas-prod"),
    endpoint: "saas-lambda/",
  })

we had to migrate to aws lambda adapter in emergency instead of monkey patch it.
)

[tclain-pillar]

Currently the only thing working is this less than ideal monkey patch:

  const path = url.pathname.slice(
    opts.endpoint.length + (opts.endpoint.endsWith("/") ? 1 : 2)
  );

[KATT]

Feel free to do a PR, this PR should guide on where to look :)

[github-actions]

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