Removing toLoweCase() on resolveUriForOAuth2 helper method

[danielreyesGL]

When trying to use /push endpoint toLowerCase() call on helper method removes case on messageId parameter and request fails because ID is not found ( due to messageId case).

[balwillSFDC]

Thank you for pointing this out! Was trying to figure out what was making my calls to the /sms/v1/messageContact/{id}/send endpoint to fail...