RabbitMQ - Add username customization (#11899)

* add username customization for rabbitmq

* add changelog for rabbitmq

* Update builtin/logical/rabbitmq/path_config_connection.go

Co-authored-by: Tom Proctor <tomhjp@users.noreply.github.com>

* updating API docs

* moved to changelog folder

Co-authored-by: Tom Proctor <tomhjp@users.noreply.github.com>

builtin/logical/rabbitmq/path_config_connection_test.go

@@ -0,0 +1,104 @@
+package rabbitmq
+
+import (
+	"context"
+	"reflect"
+	"testing"
+
+	"github.com/hashicorp/vault/sdk/logical"
+)
+
+func TestBackend_ConfigConnection_DefaultUsernameTemplate(t *testing.T) {
+	var resp *logical.Response
+	var err error
+	config := logical.TestBackendConfig()
+	config.StorageView = &logical.InmemStorage{}
+	b := Backend()
+	if err = b.Setup(context.Background(), config); err != nil {
+		t.Fatal(err)
+	}
+
+	configData := map[string]interface{}{
+		"connection_uri":    "uri",
+		"username":          "username",
+		"password":          "password",
+		"verify_connection": "false",
+	}
+	configReq := &logical.Request{
+		Operation: logical.UpdateOperation,
+		Path:      "config/connection",
+		Storage:   config.StorageView,
+		Data:      configData,
+	}
+	resp, err = b.HandleRequest(context.Background(), configReq)
+	if err != nil || (resp != nil && resp.IsError()) {
+		t.Fatalf("bad: resp: %#v\nerr:%s", resp, err)
+	}
+	if resp != nil {
+		t.Fatal("expected a nil response")
+	}
+
+	actualConfig, err := readConfig(context.Background(), config.StorageView)
+	if err != nil {
+		t.Fatalf("unable to read configuration: %v", err)
+	}
+
+	expectedConfig := connectionConfig{
+		URI:              "uri",
+		Username:         "username",
+		Password:         "password",
+		UsernameTemplate: "",
+	}
+
+	if !reflect.DeepEqual(actualConfig, expectedConfig) {
+		t.Fatalf("Expected: %#v\nActual: %#v", expectedConfig, actualConfig)
+	}
+}
+
+func TestBackend_ConfigConnection_CustomUsernameTemplate(t *testing.T) {
+	var resp *logical.Response
+	var err error
+	config := logical.TestBackendConfig()
+	config.StorageView = &logical.InmemStorage{}
+	b := Backend()
+	if err = b.Setup(context.Background(), config); err != nil {
+		t.Fatal(err)
+	}
+
+	configData := map[string]interface{}{
+		"connection_uri":    "uri",
+		"username":          "username",
+		"password":          "password",
+		"verify_connection": "false",
+		"username_template": "{{ .DisplayName }}",
+	}
+	configReq := &logical.Request{
+		Operation: logical.UpdateOperation,
+		Path:      "config/connection",
+		Storage:   config.StorageView,
+		Data:      configData,
+	}
+	resp, err = b.HandleRequest(context.Background(), configReq)
+	if err != nil || (resp != nil && resp.IsError()) {
+		t.Fatalf("bad: resp: %#v\nerr:%s", resp, err)
+	}
+	if resp != nil {
+		t.Fatal("expected a nil response")
+	}
+
+	actualConfig, err := readConfig(context.Background(), config.StorageView)
+	if err != nil {
+		t.Fatalf("unable to read configuration: %v", err)
+	}
+
+	expectedConfig := connectionConfig{
+		URI:              "uri",
+		Username:         "username",
+		Password:         "password",
+		UsernameTemplate: "{{ .DisplayName }}",
+	}
+
+	if !reflect.DeepEqual(actualConfig, expectedConfig) {
+		t.Fatalf("Expected: %#v\nActual: %#v", expectedConfig, actualConfig)
+	}
+}