Only use IndexIgnore if mod_autoindex.c is enabled/loaded.

[ghost]

Description

IndexIgnore can be used in the .htaccess only if https://httpd.apache.org/docs/current/mod/mod_autoindex.html is enabled. If not the following internal server error is thrown:

/var/www/owncloud/data/.htaccess: Invalid command 'IndexIgnore', perhaps misspelled or defined by a module not included in the server configuration

when accessing the protected folders like:

http://example.com/data/owncloud.log

Related Issue

Fixes #28307

Motivation and Context

Don't throw 500 internal server errors around if mod_autoindex is not loaded.

How Has This Been Tested?

1. Adding the code
2. Accessing the protected directories
3. See that now a 403 Forbidden is thrown instead of an internal server error

Types of changes

• Bug fix (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 change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[ghost]

Same for user_ldap in owncloud/user_ldap#112

[felixboehm]

yes, makes sense.

[ghost]

Backports to stable10, 9.1 and 9 in #28591, #28592 and #28593