ENH: Add in support for Authorization bearer token - AuthTokenProvider

[rbygrave]

With this we can register a AuthTokenProvider that can be used to make a request to obtain a token and register it along with it's valid time. All requests (apart from the request to obtain the token) get this token applied to the request automatically - the token is obtained/refreshed automatically.

Implement AuthTokenProvider

  static class MyAuthTokenProvider implements AuthTokenProvider {

    @Override
    public AuthToken obtainToken(HttpClientRequest tokenRequest) {
      AuthTokenResponse res = tokenRequest
        .url("https://foo/token")
        .body(authRequestBean())
        .post()
        .bean(AuthTokenResponse.class);

      String accessToken = res.getAccessToken();
      Instant validUntil = Instant.now().plusSeconds(res.getExpiresIn()).minusSeconds(60);

      return AuthToken.of(accessToken, validUntil);
    }
  }

Register the AuthTokenProvider

Use withAuthTokenProvider() to register the AuthTokenProvider implementation.

    HttpClientContext ctx = HttpClientContext.newBuilder()
      .withBaseUrl("https://foo/api")
      .withAuthTokenProvider(new MyAuthTokenProvider())  // <----- HERE
      .withBodyAdapter(new JacksonBodyAdapter(objectMapper))
      .withRequestListener(new RequestLogger())
      .build();

Use HttpClientContext as normal

Just use HttpClientContext to make requests as normal. These requests will automatically get the Authorization header added with the Bearer token.

    Bazz response = ctx.request()
      .path(path)
      .header("my-header", "to-fa-ti")   // the Authorization header with bearer token will be added automatically
      .body(requestPayload)
      .post()
      .bean(Bazz.class);