Add fluent AssertJ-style assertions for RecordedRequests from OkHttp MockWebServer

[sleberknight]

Instead of this:

var request = takeRequiredRequest(mockWebServer);
assertThat(request.getMethod()).isEqualTo("GET");
assertThat(request.getPath()).isEqualTo("/status");

I want to do this:

assertThatRequiredRequest(mockWebServer)
    .hasMethod("GET")
    .hasPath("/status");

and so on. Since request methods are well-known, perhaps provide dedicated methods:

assertThatRequiredRequest(mockWebServer)
    .isPOST()
    .hasPath("/users")
    .hasBody("{ ... }");

The other things to probably include are:

• body
• body size
• header(s)
• request URI
• ...