Section for backward-incompatible changes in the changelog (#8941)

In addition to the existing "fixes" and "implements" sections.

Author: akuzm

scripts/changelog/generate.sh

@@ -40,6 +40,7 @@ echo "Building CHANGELOG"
     echo "**Highlighted features in TimescaleDB v${RELEASE_NEXT}**"
     echo "* "
     echo ""
+    echo_changelog '**Backward-Incompatible Changes**' '^Backward-Incompatible Change:'
     echo_changelog '**Features**' '^Implements:'
     echo_changelog '**Bugfixes**' '^Fixes:'
     echo_gucs $RELEASE_PREVIOUS $RELEASE_BRANCH

scripts/changelog/template.rfc822

@@ -1,3 +1,5 @@
+Backward-Incompatible Change: #NNNNN <one line description of the feature>
+
 Implements: #NNNNN <one line description of the feature>
 
 Fixes: #NNNNN <one line description of the Issue>

scripts/check_changelog_format.py

@@ -69,7 +69,12 @@ def get_referenced_issues(pr_number):
 
 # Check if a line matches any of the specified patterns
 def is_valid_line(line):
-    patterns = [r"^Fixes:\s*.*$", r"^Implements:\s*.*$", r"^Thanks:\s*.*$"]
+    patterns = [
+        r"^Fixes:\s*.*$",
+        r"^Implements:\s*.*$",
+        r"^Thanks:\s*.*$",
+        r"^Backward-Incompatible Change:\s*.*$",
+    ]
     for pattern in patterns:
         if re.match(pattern, line):
             return True