FEATURE: Allow excluding uploads from min post length requirement (#31194)

Currently, the markdown for uploads is counted towards post minimum length requirements. This change introduces a site setting `prevent_uploads_only_posts` which can be flipped to exclude upload segments from the calculation.

config/locales/server.en.yml

@@ -1743,6 +1743,7 @@ en:
     support_mixed_text_direction: "Support mixed left-to-right and right-to-left text directions"
     min_post_length: "Minimum allowed post length in characters (excluding personal messages)"
     min_first_post_length: "Minimum allowed first post (topic body) length (excluding personal messages)"
+    prevent_uploads_only_posts: "Don't count upload markdown code when checking for min post length"
     min_personal_message_post_length: "Minimum allowed post length in characters for messages (both first post and replies)"
     max_post_length: "Maximum allowed post length in characters"
     topic_featured_link_enabled: "Allows users to associate a feature link with their topics. When turned on, topics can have a highlighted link attached, which is publicly visible and can be edited if the user has sufficient permissions. The feature link can enhance a topic's comprehensibility by providing related additional content."

config/site_settings.yml

@@ -916,6 +916,9 @@ posting:
       ja: 8
       zh_CN: 8
       zh_TW: 8
+  prevent_uploads_only_posts:
+    client: true
+    default: false
   min_personal_message_post_length:
     client: true
     min: 1