fix: handle @ in display name when using MailHelper.StringToEmailAddress (#903)

* Update MailHelper.cs

fix email regex to allow email addresses in the display name.

Input: [email protected] <[email protected]>
Expected:
-NameGroup: [email protected]
-EmailGroup: [email protected]

Initial:
-NameGroup: {empty string}
-EmailGroup: 	[email protected] <[email protected]
Result: A match is found, therefore there is no error caught and email string is bad

After:
-NameGroup: [email protected]
-EmailGroup: [email protected]
Result: Success!

Other test cases:
-<[email protected]> SUCCESS
[email protected] SUCCESS
-username <[email protected]> SUCCESS
-username <usernameexample.com> NO MATCH (SUCCESS)

Author: Fieora

src/SendGrid/Helpers/Mail/MailHelper.cs

@@ -17,7 +17,7 @@ public class MailHelper
         private const string NameGroup = "name";
         private const string EmailGroup = "email";
         private static readonly Regex Rfc2822Regex = new Regex(
-            $@"(?:(?<{NameGroup}>)(?<{EmailGroup}>[^\<]*@.*[^\>])|(?<{NameGroup}>[^\<]*)\<(?<{EmailGroup}>.*@.*)\>)",
+            $@"(?:(?<{NameGroup}>[^\<]*)\<(?<{EmailGroup}>.*@.*)\>|(?<{NameGroup}>)(?<{EmailGroup}>[^\<]*@.*[^\>]))",
             RegexOptions.ECMAScript);
 
         /// <summary>

tests/SendGrid.Tests/Integration.cs

@@ -6126,6 +6126,18 @@ public async Task TestRetryBehaviourSucceedsOnSecondAttempt()
             Assert.Equal(HttpStatusCode.OK, result.StatusCode);
         }
 
+        [Theory]
+        [InlineData("first last <[email protected]>", "first last", "[email protected]")]
+        [InlineData("<[email protected]>", "", "[email protected]")]
+        [InlineData("[email protected]", "", "[email protected]")]
+        [InlineData("[email protected] <[email protected]>", "[email protected]", "[email protected]")]
+        public void TestStringToEmailAddress(string input, string expectedName, string expectedEmailAddress)
+        {
+            var actual = MailHelper.StringToEmailAddress(input);
+
+            Assert.True(actual.Name == expectedName && actual.Email == expectedEmailAddress);
+        }
+        
         /// <summary>
         /// Tests the conditions in issue #670.
         /// </summary>