☕ add a dependency-injection examples folder for the next release and some improvements

Former-commit-id: 040168afb7caf808618f7da5e68ae8eb01cb7170

_examples/dependency-injection/basic/middleware/main_test.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/kataras/iris/v12/httptest"
+)
+
+func TestDependencyInjectionBasic_Middleware(t *testing.T) {
+	app := newApp()
+
+	e := httptest.New(t, app)
+	e.POST("/42").WithJSON(testInput{Email: "my_email"}).Expect().
+		Status(httptest.StatusOK).
+		JSON().Equal(testOutput{ID: 42, Name: "my_email"})
+
+	// it should stop the execution at the middleware and return the middleware's status code,
+	// because the error is `ErrStopExecution`.
+	e.POST("/42").WithJSON(testInput{Email: "invalid"}).Expect().
+		Status(httptest.StatusAccepted).Body().Empty()
+
+	// it should stop the execution at the middleware and return the error's text.
+	e.POST("/42").WithJSON(testInput{Email: "error"}).Expect().
+		Status(httptest.StatusConflict).Body().Equal("my_error")
+}