Consolidate API

[overheadhunter]

This removes two public methods from the AuthorizationCodeGrant (which is still @ApiStatus.Experimental). Both are merely convenience methods and can easily be replaced:

tiny-oauth2-client/src/main/java/io/github/coffeelibs/tinyoauth2client/AuthorizationCodeGrant.java

Lines 131 to 133 in e264795

	public CompletableFuture<HttpResponse<String>> authorizeAsync(@BlockingExecutor Executor executor, Consumer<URI> browser, String... scopes) {
	return authorizeAsync(HttpClient.newBuilder().executor(executor).build(), browser, scopes);
	}

and

tiny-oauth2-client/src/main/java/io/github/coffeelibs/tinyoauth2client/AuthorizationCodeGrant.java

Lines 175 to 177 in e264795

	public HttpResponse<String> authorize(Consumer<URI> browser, String... scopes) throws IOException, InterruptedException {
	return authorize(HttpClient.newHttpClient(), browser, scopes);
	}

The new paradigm for the library consumer is to always pass an HttpClient instance.

[infeo]

In https://github.com/coffeelibs/tiny-oauth2-client/pull/8/files#diff-0c4a310c689eae40addbab8bb9b02a103bc0c91b38d768e51ac4d8f296624a20R128, we say that a single Thread executor is used. This is not true, the executor is the ForkJoinPool.commonPool(). Can you also fix that?