[ci] Add undocumented C++ API change checkbox and auto-label (#14317)

.github/PULL_REQUEST_TEMPLATE.md

@@ -6,8 +6,9 @@
 
 - [ ] Bugfix (non-breaking change which fixes an issue)
 - [ ] New feature (non-breaking change which adds functionality)
-- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
-- [ ] Developer breaking change (an API change that could break external components)
+- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected) — [policy](https://developers.esphome.io/contributing/code/#what-constitutes-a-c-breaking-change)
+- [ ] Developer breaking change (an API change that could break external components) — [policy](https://developers.esphome.io/contributing/code/#what-is-considered-public-c-api)
+- [ ] Undocumented C++ API change (removal or change of undocumented public methods that lambda users may depend on) — [policy](https://developers.esphome.io/contributing/code/#c-user-expectations)
 - [ ] Code quality improvements to existing code or addition of tests
 - [ ] Other
 

.github/scripts/auto-label-pr/constants.js

@@ -27,6 +27,7 @@ module.exports = {
     'new-feature',
     'breaking-change',
     'developer-breaking-change',
+    'undocumented-api-change',
     'code-quality',
     'deprecated-component'
   ],

.github/scripts/auto-label-pr/detectors.js

@@ -238,6 +238,7 @@ async function detectPRTemplateCheckboxes(context) {
     { pattern: /- \[x\] New feature \(non-breaking change which adds functionality\)/i, label: 'new-feature' },
     { pattern: /- \[x\] Breaking change \(fix or feature that would cause existing functionality to not work as expected\)/i, label: 'breaking-change' },
     { pattern: /- \[x\] Developer breaking change \(an API change that could break external components\)/i, label: 'developer-breaking-change' },
+    { pattern: /- \[x\] Undocumented C\+\+ API change \(removal or change of undocumented public methods that lambda users may depend on\)/i, label: 'undocumented-api-change' },
     { pattern: /- \[x\] Code quality improvements to existing code or addition of tests/i, label: 'code-quality' }
   ];