DEV: Move discourse-chat to the core repo. (#18776)

As part of this move, we are also renaming `discourse-chat` to `chat`.

plugins/chat/lib/validators/chat_allow_uploads_validator.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+class ChatAllowUploadsValidator
+  def initialize(opts = {})
+    @opts = opts
+  end
+
+  def valid_value?(value)
+    return false if value == "t" && prevent_enabling_chat_uploads?
+    true
+  end
+
+  def error_message
+    if prevent_enabling_chat_uploads?
+      I18n.t("site_settings.errors.chat_upload_not_allowed_secure_uploads")
+    end
+  end
+
+  def prevent_enabling_chat_uploads?
+    SiteSetting.secure_uploads && !GlobalSetting.allow_unsecure_chat_uploads
+  end
+end

plugins/chat/lib/validators/chat_default_channel_validator.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class ChatDefaultChannelValidator
+  def initialize(opts = {})
+    @opts = opts
+  end
+
+  def valid_value?(value)
+    !!(value == "" || ChatChannel.find_by(id: value.to_i)&.public_channel?)
+  end
+
+  def error_message
+    I18n.t("site_settings.errors.chat_default_channel")
+  end
+end

plugins/chat/lib/validators/direct_message_enabled_groups_validator.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class DirectMessageEnabledGroupsValidator
+  def initialize(opts = {})
+    @opts = opts
+  end
+
+  def valid_value?(val)
+    val.present? && val != ""
+  end
+
+  def error_message
+    I18n.t("site_settings.errors.direct_message_enabled_groups_invalid")
+  end
+end