Add before save callback to truncate email if > 255 chars

What does this MR do and why?

Relates to #409653 (closed)

In cases where email length is > 255 chars, we modify the email to set it within limit and allow the note creation.

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Related to #409653 (closed)

app/models/notes/note_metadata.rb

@@ -7,11 +7,10 @@ class NoteMetadata < ApplicationRecord
     EMAIL_PARTICIPANT_LENGTH = 255
 
     belongs_to :note, inverse_of: :note_metadata
-    validates :email_participant, length: { maximum: EMAIL_PARTICIPANT_LENGTH }
 
     alias_attribute :external_author, :email_participant
 
-    before_validation :ensure_email_participant_length
+    before_save :ensure_email_participant_length, if: ->(note_metadata) { email_participant && email_participant.length > EMAIL_PARTICIPANT_LENGTH }
 
     private
 
@@ -20,7 +19,9 @@ def ensure_email_participant_length
 
       email_prefix, email_suffix = email_participant.split('@')
 
-      allowed_prefix_length = EMAIL_PARTICIPANT_LENGTH - email_suffix.length - 1 # 1 is for '@'
+      email_suffix_length = email_suffix ? email_suffix.length : 0
+
+      allowed_prefix_length = EMAIL_PARTICIPANT_LENGTH - email_suffix_length - 1 # 1 is for '@'
 
       self.email_participant = "#{email_prefix[0...allowed_prefix_length]}@#{email_suffix}"
     end