Fix: Email and username trimming and invitation validation (#58442)

* fix: email and username trimming and invitation validation

* Trim leading and trailing whitespaces from email and username on signup

* Check whether the provided email address is the same as where the invitation sent

* Align tests

Co-authored-by: Mihaly Gyongyosi <mgyongyosi@users.noreply.github.com>

pkg/api/utils.go

@@ -1,9 +1,25 @@
 package api
 
-import "encoding/json"
+import (
+	"encoding/json"
+	"net/mail"
+)
 
 func jsonMap(data []byte) (map[string]string, error) {
 	jsonMap := make(map[string]string)
 	err := json.Unmarshal(data, &jsonMap)
 	return jsonMap, err
 }
+
+func ValidateAndNormalizeEmail(email string) (string, error) {
+	if email == "" {
+		return "", nil
+	}
+
+	e, err := mail.ParseAddress(email)
+	if err != nil {
+		return "", err
+	}
+
+	return e.Address, nil
+}