Merge branch 'main' into glitch-soc/merge-upstream

Conflicts:
- `app/models/custom_emoji.rb`:
  Not a real conflict, just upstream changing a line too close to
  a glitch-soc-specific validation.
  Applied upstream changes.
- `app/models/public_feed.rb`:
  Not a real conflict, just upstream changing a line too close to
  a glitch-soc-specific parameter documentation.
  Applied upstream changes.

app/models/custom_emoji.rb

@@ -31,6 +31,7 @@ class CustomEmoji < ApplicationRecord
   SCAN_RE = /(?<=[^[:alnum:]:]|\n|^)
     :(#{SHORTCODE_RE_FRAGMENT}):
     (?=[^[:alnum:]:]|$)/x
+  SHORTCODE_ONLY_RE = /\A#{SHORTCODE_RE_FRAGMENT}\z/
 
   IMAGE_MIME_TYPES = %w(image/png image/gif image/webp).freeze
 
@@ -44,7 +45,7 @@ class CustomEmoji < ApplicationRecord
   validates_attachment :image, content_type: { content_type: IMAGE_MIME_TYPES }, presence: true
   validates_attachment_size :image, less_than: LIMIT, unless: :local?
   validates_attachment_size :image, less_than: LOCAL_LIMIT, if: :local?
-  validates :shortcode, uniqueness: { scope: :domain }, format: { with: /\A#{SHORTCODE_RE_FRAGMENT}\z/ }, length: { minimum: 2 }
+  validates :shortcode, uniqueness: { scope: :domain }, format: { with: SHORTCODE_ONLY_RE }, length: { minimum: 2 }
 
   scope :local, -> { where(domain: nil) }
   scope :remote, -> { where.not(domain: nil) }