Add BearerAuth middleware

[mdlkxzmcp]

Adds a Tesla.Middleware.BearerAuth middleware.

Basically, I had to use the bearer auth method, but Tesla doesn't have a middleware for it. So here is my small contribution :)

Wanted to include a wiki article on it in the module docs, but it's only listed as a part of Oauth...

[teamon]

Hi @mdlkxzmcp

I appreciate the contribution!

If I understand correctly, what this middlewares does when used like this:

Tesla.client [
  {Tesla.Middleware.BearerAuth, Map.merge(%{token: token}, opts))}
]

is essentially the same as using Tesla.Middleware.Headers directly:

Tesla.client [
  {Tesla.Middleware.Headers, [{"authorization", "Bearer #{token}}]}
]

In general, adding such new middleware shouldn't be needed (as one can use the more generic Headers middleware).
However, we do include BaseAuth middleware for a nicer user experience, and I think it doesn't hurt to have a BearerAuth too.

Having said that, I'd like to add as little code as possible, as each line of code needs to be maintained for a long time. And this applies also to tests.

I'd suggest a minimal implementation, something along (not tested)

def call(env, next, opts) do
  token = Keyword.fetch!(opts, :token)

  env
  |> Tesla.put_headers({"authorization", "Bearer #{token}})
  |> Tesla.run(next)
end

and then just one or two test cases testing the middleware in isolation.

Please do let me know if you have any questions regarding all that.

[mdlkxzmcp]

Hey @teamon!

It is indeed essentially the same as setting the header, however, I felt that, since it's related to authentication, it would be beneficial to have it as its own middleware.

I'm totally ok with rewriting it to be simpler like you showed. I simply wanted to follow the logic from other middleware modules :)

Should have a rewrite by the end of the day :>