Added entrypoint hooks for your own custom scripts (#1964)

* Added entrypoint hooks for your own custom scripts

Signed-off-by: Dennis Vestergaard Værum <github@varum.dk>

* Small changes:
- Only execute shell-scripts (mening files ending with .sh)
- Sort the files before executing them, had forgotten 😅
- Added a message when a hook script finish
- Added prefix arror to message to show the are related

Signed-off-by: Dennis Vestergaard Værum <github@varum.dk>

* Show in the search msg that it only searches for '*.sh' files

Signed-off-by: Dennis Vestergaard Værum <github@varum.dk>

* Fixed spelling mistake

Co-authored-by: J0WI <J0WI@users.noreply.github.com>
Signed-off-by: Dennis Værum <6872940+dvaerum@users.noreply.github.com>

* Updated the `README.md` file

Signed-off-by: Dennis Vestergaard Værum <github@varum.dk>

* change from using find to using a for-loop to located the `.sh` files

Signed-off-by: Dennis Vestergaard Værum <github@varum.dk>

* Fix bug - that would make docker-entrypoint.sh failed, hook folders was empty

Signed-off-by: Dennis Vestergaard Værum <github@varum.dk>

---------

Signed-off-by: Dennis Vestergaard Værum <github@varum.dk>
Signed-off-by: Dennis Værum <6872940+dvaerum@users.noreply.github.com>
Co-authored-by: J0WI <J0WI@users.noreply.github.com>

Dockerfile-alpine.template

@@ -99,6 +99,11 @@ RUN { \
     } > "${PHP_INI_DIR}/conf.d/nextcloud.ini"; \
     \
     mkdir /var/www/data; \
+    mkdir -p /docker-entrypoint-hooks.d/pre-installation \
+             /docker-entrypoint-hooks.d/post-installation \
+             /docker-entrypoint-hooks.d/pre-upgrade \
+             /docker-entrypoint-hooks.d/post-upgrade \
+             /docker-entrypoint-hooks.d/before-starting; \
     chown -R www-data:root /var/www; \
     chmod -R g=u /var/www