feat: add customize content type parsers for api plugin

[scott1028]

This PR allows users to extend supported contentType for native API plugin.
I follow https://redwoodjs.com/docs/docker#using-the-server-file, but it doesn't work.

    ...
  await server.register(redwoodFastifyAPI, {          <-- work after remove "await"
    redwood: {
      apiRootPath,
      fastGlobOptions: {
        ignore: ['**/dist/functions/graphql.js'],
      },
    },
  })
   ...

  // This doesn't work after a "await server.register(...)"
  server.addContentTypeParser('text/csv', { parseAs: 'string' }, (request, body, done) => {
    const csvData = body.split('\n').map(row => row.split(','))
    done(null, csvData)
  })

• ref: https://fastify.dev/docs/v2.15.x/Documentation/ContentTypeParser/#content-type-parser
• ref: https://redwoodjs.com/docs/docker#using-the-server-file
• ref: addContentTypeParser doesn't work well after await register fastify/fastify#5401
• ref: https://fastify.dev/docs/latest/Reference/Plugins/#asyncawait

[Tobbe]

Thanks for your PR @scott1028 I'm sorry no one got back to you sooner. We'll discuss this internally and see who can help move this forward

[scott1028]

Thanks for your PR @scott1028 I'm sorry no one got back to you sooner. We'll discuss this internally and see who can help move this forward

Thanks for your reply :)

[Tobbe]

@scott1028 I found someone who can look into this. He's busy with other things right now, but will get to this when he has some more time available

[Josh-Walker-GM]

Hey @scott1028 👋 Again sorry for the radio silence on this. I'll get to this one in the next day or two