Allows to inject something into the default content policy. This is for
example useful when you're injecting Javascript code into a view belonging
to another controller and cannot modify its Content-Security-Policy itself.
Note that the adjustment is only applied to applications that use AppFramework
controllers.
To use this from your `app.php` use `\OC::$server->getContentSecurityPolicyManager()->addDefaultPolicy($policy)`,
$policy has to be of type `\OCP\AppFramework\Http\ContentSecurityPolicy`.
To test this add something like the following into an `app.php` of any enabled app:
```
$manager = \OC::$server->getContentSecurityPolicyManager();
$policy = new \OCP\AppFramework\Http\ContentSecurityPolicy(false);
$policy->addAllowedFrameDomain('asdf');
$policy->addAllowedScriptDomain('yolo.com');
$policy->allowInlineScript(false);
$manager->addDefaultPolicy($policy);
$policy = new \OCP\AppFramework\Http\ContentSecurityPolicy(false);
$policy->addAllowedFontDomain('yolo.com');
$manager->addDefaultPolicy($policy);
$policy = new \OCP\AppFramework\Http\ContentSecurityPolicy(false);
$policy->addAllowedFrameDomain('banana.com');
$manager->addDefaultPolicy($policy);
```
If you now open the files app the policy should be:
```
Content-Security-Policy:default-src 'none';script-src yolo.com 'self' 'unsafe-eval';style-src 'self' 'unsafe-inline';img-src 'self' data: blob:;font-src yolo.com 'self';connect-src 'self';media-src 'self';frame-src asdf banana.com 'self'
```
When returning a 500 statuscode external applications may interpret this as an error instead of handling this more gracefully. This will now make return a 401 thus.
Fixes https://github.com/owncloud/core/issues/17742
remove methodannotationreader namespace
fix namespace for server container
fix tests
fail if with cors credentials header is set to true, implement a reusable preflighted cors method in the controller baseclass, make corsmiddleware private and register it for every request
remove uneeded local in cors middleware registratio
dont uppercase cors to easily use it from routes
fix indention
comment fixes
explicitely set allow credentials header to false
dont depend on better controllers PR, fix that stuff later
split cors methods to be in a seperate controller for exposing apis
remove protected definitions from apicontroller since controller has it