Allow multiple valid webhook URL FQDNs

Based on research/testing, it appears that both of these two
FQDNs are interchangeable:

- outlook.office.com
- outlook.office365.com

This commit makes the following changes to accept either
FQDN as a valid webhook prefix:

- update the isValidWebhookURL validation
  function to accept either one as a valid webhook prefix

- update the TestTeamsClientSend table test to include
  outlook.office365.com variations of existing test cases
  specific to outlook.office.com

refs dasrick#3

send.go

@@ -82,9 +82,11 @@ func isValidWebhookURL(webhookURL string) (bool, error) {
 		return false, err
 	}
 	// only pass MS teams webhook URLs
-	hasPrefix := strings.HasPrefix(webhookURL, "https://outlook.office.com/webhook/")
-	if !hasPrefix {
-		err = errors.New("unvalid ms teams webhook url")
+	switch {
+	case strings.HasPrefix(webhookURL, "https://outlook.office.com/webhook/"):
+	case strings.HasPrefix(webhookURL, "https://outlook.office365.com/webhook/"):
+	default:
+		err = errors.New("invalid ms teams webhook url")
 		return false, err
 	}
 	return true, nil

send_test.go

@@ -33,7 +33,7 @@ func TestTeamsClientSend(t *testing.T) {
 			resError:  nil,
 			error:     &url.Error{},
 		},
-		// invalid webhookURL - missing pefix in (https://outlook.office.com...) URL
+		// invalid webhookURL - missing prefix in webhook URL
 		{
 			reqURL:    "",
 			reqMsg:    emptyMessage,
@@ -49,6 +49,14 @@ func TestTeamsClientSend(t *testing.T) {
 			resError:  errors.New("pling"),
 			error:     &url.Error{},
 		},
+		// invalid httpClient.Do call
+		{
+			reqURL:    "https://outlook.office365.com/webhook/xxx",
+			reqMsg:    emptyMessage,
+			resStatus: 200,
+			resError:  errors.New("pling"),
+			error:     &url.Error{},
+		},
 		// invalid response status code
 		{
 			reqURL:    "https://outlook.office.com/webhook/xxx",
@@ -57,6 +65,14 @@ func TestTeamsClientSend(t *testing.T) {
 			resError:  nil,
 			error:     errors.New(""),
 		},
+		// invalid response status code
+		{
+			reqURL:    "https://outlook.office365.com/webhook/xxx",
+			reqMsg:    emptyMessage,
+			resStatus: 400,
+			resError:  nil,
+			error:     errors.New(""),
+		},
 		// valid
 		{
 			reqURL:    "https://outlook.office.com/webhook/xxx",
@@ -65,6 +81,14 @@ func TestTeamsClientSend(t *testing.T) {
 			resError:  nil,
 			error:     nil,
 		},
+		// valid
+		{
+			reqURL:    "https://outlook.office365.com/webhook/xxx",
+			reqMsg:    emptyMessage,
+			resStatus: 200,
+			resError:  nil,
+			error:     nil,
+		},
 	}
 	for _, test := range tests {
 		client := NewTestClient(func(req *http.Request) (*http.Response, error) {