don't count bio metadata against bio length on server

app/models/account.rb

@@ -60,7 +60,7 @@ class Account < ApplicationRecord
   validates :username, format: { with: /\A[a-z0-9_]+\z/i }, uniqueness: { scope: :domain, case_sensitive: false }, length: { maximum: 30 }, if: -> { local? && will_save_change_to_username? }
   validates_with UnreservedUsernameValidator, if: -> { local? && will_save_change_to_username? }
   validates :display_name, length: { maximum: 30 }, if: -> { local? && will_save_change_to_display_name? }
-  validates :note, length: { maximum: 500 }, if: -> { local? && will_save_change_to_note? }
+  validate :note_length_does_not_exceed_length_limit, if: -> { local? && will_save_change_to_note? }
 
   # Timelines
   has_many :stream_entries, inverse_of: :account, dependent: :destroy
@@ -251,6 +251,22 @@ class Account < ApplicationRecord
     self.public_key  = keypair.public_key.to_pem
   end
 
+  YAML_START = "---\r\n"
+  YAML_END = "\r\n...\r\n"
+
+  def note_length_does_not_exceed_length_limit
+    note_without_metadata = note
+    if note.start_with? YAML_START
+      idx = note.index YAML_END
+      unless idx.nil?
+        note_without_metadata = note[(idx + YAML_END.length) .. -1]
+      end
+    end
+    if note_without_metadata.mb_chars.grapheme_length > 500
+      errors.add(:note, "can't be longer than 500 graphemes")
+    end
+  end
+
   def normalize_domain
     return if local?