Add test for handling special characters in email fields

[DhiraPT]

Added a new test case testSpecialCharactersInFields to verify the correct handling of special characters, emojis, and HTML entities in email subject and content.

• Updated EmailSenderTest with the new test method to ensure proper parsing and encoding of special characters in email fields.
• Validates UTF-8 compatibility for subjects and content with emojis and symbols.
• Focused on Sendgrid email conversion logic but extensible to other services in the future.

[github-actions]

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