feat(holidays): migrate school holidays to OpenHolidays data

Migrate school holiday data from manually maintained YAML files to
automated generation from OpenHolidays Git submodule, expanding
coverage from 8 to 33 countries.

Implementation:
- Add openholidaysapi.data as Git submodule
- Create fetch-school-holidays.mjs to parse CSV files from submodule
- Generate subdivision entries using full names from subdivisions.csv
- Merge generated SH data with existing YAML PH data
- Add export validation for index.js

Migrated countries (8): at, be, de, fr, hr, hu, lu, ro
New countries (25): ad, al, bg, by, ch, ci, cz, dk, ee, es, ie, it,
li, lt, lv, mc, md, mt, mx, nl, pl, pt, rs, si, sk, sm, za

Tests updated from 2014-2015 to 2024-2025 timeframe.
Update data: node scripts/fetch-school-holidays.mjs

Author: KristjanESPERANTO

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "submodules/YoHours"]
 	path = submodules/YoHours
 	url = https://framagit.org/PanierAvide/YoHours.git
+[submodule "submodules/openholidaysapi.data"]
+	path = submodules/openholidaysapi.data
+	url = https://github.com/openpotato/openholidaysapi.data.git

CONTRIBUTING.md

@@ -29,12 +29,13 @@ We use a branching model inspired by Gitflow:
 When the `develop` branch is deemed ready for a new release:
 
 1.  A maintainer prepares the release in a `release/` branch based on `develop`.
-2.  The maintainer runs `make release-prepare` locally.
-2.  The maintainer decides if a release candidate should be released, if rc `npx commit-and-tag-version --prerelease=rc` should be run locally, if not `make release-local` should be run. In case a maintainer does not have a separate OpenSSH/OpenPGP key for releases, they can use their regular signing key. The maintainer pushes the signed git tag to their repo fork.
-2.  This pull request will be reviewed and then merged into `develop`
-3.  The maintainer creates a new pull request from `develop` to `main`.
-5.  ypid who is currently the only one who can release to npmjs.com gets assigned the pull requests, pulls the signed git tag and runs `make release-publish` on their machine and finally merges the pull request.
-4.  ypid creates a release on GitHub and marks it as latest.
+2.  The maintainer updates school holiday data: `node scripts/fetch-school-holidays.mjs` and commits any changes.
+3.  The maintainer runs `make release-prepare` locally.
+4.  The maintainer decides if a release candidate should be released, if rc `npx commit-and-tag-version --prerelease=rc` should be run locally, if not `make release-local` should be run. In case a maintainer does not have a separate OpenSSH/OpenPGP key for releases, they can use their regular signing key. The maintainer pushes the signed git tag to their repo fork.
+5.  This pull request will be reviewed and then merged into `develop`
+6.  The maintainer creates a new pull request from `develop` to `main`.
+7.  ypid who is currently the only one who can release to npmjs.com gets assigned the pull requests, pulls the signed git tag and runs `make release-publish` on their machine and finally merges the pull request.
+8.  ypid creates a release on GitHub and marks it as latest.
 
 ## Translation Contributions
 

README.md

@@ -611,17 +611,13 @@ Almost everything from opening_hours definition is supported, as well as some ex
 
 - Support for school holidays (`SH 10:00-14:00`).
 
-  - Countries with SH definition:
-
-    - Austria (national until 2024, regional until 2021)
-    - Belgium (good until 2026)
-    - Croatia (good until 2022–2023)
-    - France (good until 2025)
-    - Germany, see [hc] and [scripts/update_german_sh.mjs](scripts/update_german_sh.mjs) (good until 2026)
-    - Greece (good until 2020)
-    - Hungary (good until 2024–2025)
-    - Luxembourg (good until 2025–2026)
-    - Romania (good until 2021)
+  School holidays are automatically sourced from the [OpenHolidays API](https://openholidaysapi.org) for 33 countries (from 2020 onwards). Update data by running:
+
+  ```bash
+  node scripts/fetch-school-holidays.mjs
+  ```
+
+  For details see [src/holidays/README.md](src/holidays/README.md).
 
 - There can be two cases which need to be separated (this applies for PH and SH):
 
@@ -876,7 +872,6 @@ Edit: This does also work on npmjs in this short version … -->
 [ohlib.library-api]: #library-api
 [ohlib.npmjs]: https://www.npmjs.org/package/opening_hours
 [ohlib.github]: https://github.com/opening-hours/opening_hours.js
-[hc]: https://gitlab.com/ypid/hc
 [evaluation tool]: https://openingh.openstreetmap.de/evaluation_tool/
 [ph-ar]: https://en.wikipedia.org/wiki/Public_holidays_in_Argentina
 [ph-at]: https://de.wikipedia.org/wiki/Feiertage_in_%C3%96sterreich

eslint.config.mjs

@@ -6,7 +6,7 @@ import stylistic from '@stylistic/eslint-plugin'
 import tseslint from 'typescript-eslint'
 
 export default defineConfig([
-  globalIgnores(['build/*', 'submodules/*', '**/yohours_model.js']),
+  globalIgnores(['build/*', 'submodules/*', '**/yohours_model.js', 'src/holidays/generated-openholidays.js']),
   {
     files: ['**/*.js', '**/*.mjs'],
     extends: [js.configs.recommended],

rollup.config.mjs

@@ -3,18 +3,10 @@ import nodeResolve from '@rollup/plugin-node-resolve';
 import terser from '@rollup/plugin-terser';
 import yaml from '@rollup/plugin-yaml';
 
-function recursivelyDeleteNominatimUrl(data) {
-    if (typeof data === 'object') {
-        Object.values(data).forEach(recursivelyDeleteNominatimUrl);
-    }
-    delete data._nominatim_url;
-    return data;
-}
-
+// YAML plugin only for non-holiday files (e.g., word_error_correction.yaml)
+// Holiday data now comes from generated-openholidays.js
 const yamlPlugin = yaml({
-    transform(data) {
-        return recursivelyDeleteNominatimUrl(data);
-    }
+    include: ['**/*.yaml', '!**/holidays/*.yaml']
 });
 
 const terserConfig = {