feat: Implement EoL warning banner for unsupported releases

Added a warning banner for outdated documentation.

Signed-off-by: Josh <josh.t.richards@gmail.com>

Author: joshtrichards

conf.py

@@ -87,6 +87,19 @@ def generateVersionsDocs(current_docs):
 edit_on_github_project = 'nextcloud/documentation'
 edit_on_github_branch = 'master'
 
+# Automatically add EoL warning banner to docs for unsupported releases
+if (version.isdigit() and version < version_start):
+    rst_prolog = """.. danger::
+        **OUTDATED DOCUMENTATION**
+    
+            *You are viewing documentation for a retired version of Nextcloud software.
+            Do not follow these instructions for current releases.*
+
+        **To ensure you have the most reliable and up-to-date guidance,
+        please visit the** `official Nextcloud Documentation library
+        <https://docs.nextcloud.com/>`_.
+    """
+
 # user starts in light mode
 default_dark_mode = False