Add HTTP basic authentication endpoint

app.rb

@@ -217,6 +217,25 @@ helpers do
       JSON.generate(obj, opts:)
     end
   end
+
+  def protected! hidden = false
+    return if authorized?
+
+    if hidden
+      halt 404, "Not Found"
+    else
+      headers["WWW-Authenticate"] = 'Basic realm="Restricted Area"'
+      halt 401, "Unauthorized"
+    end
+  end
+
+  def authorized?
+    @auth ||= Rack::Auth::Basic::Request.new(request.env)
+    @auth.provided? and
+      @auth.basic? and
+      @auth.credentials and
+      @auth.credentials == ["qwer", "asdf"]
+  end
 end
 
 get "/" do
@@ -382,3 +401,15 @@ get "/chunked/:delay" do
     out << "Hello, world!\n"
   end
 end
+
+route :delete, :get, :patch, :post, :put, "/auth/basic", provides: "json" do
+  pretty = params.key? :pretty
+
+  if params.key? :hidden
+    protected! hidden: true
+  else
+    protected!
+  end
+
+  json({authenticated: true, user: @auth.username}, pretty:)
+end