feat: add clearMetadata() method to provide privacy options when using imagick handler

[michalsn]

Description
This PR introduces a flexible clearMetadata() method that allows for convenient and configurable removal of image metadata, which can improve privacy.

While metadata such as EXIF is automatically stripped when using the GD image handler, this method is specifically designed for use with the Imagick handler, where metadata is preserved by default.

To ensure API consistency, the BaseHandler also provides the same clearMetadata() method, but it is implemented as a no-op (does nothing).

Reference: #6149 (comment)

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[michalsn]

Okay, I guess I have to revisit the data I'm trying to strip. I will look for an example JPEG (preferably small) with some ready EXIF data because our default PNG acts differently depending on the OS.

This will have to wait, probably for tomorrow.

[michalsn]

Okay, apparently I was too optimistic to introduce various options for deleting metadata and we have to make it work only with simple stripping of all the data. When imagick shows properties like exif:DateTime, it's parsed from the binary profile for display, but deletion via deleteImageProperty() doesn't actually modify the binary EXIF block.

I thought I could make it more flexible, but it will not work the same for all images… Now, after the changes, we will have the same functionality for both handlers - just stripping all the metadata.

[michalsn]

@paulbalandan Now I'm wondering, shouldn't we also modify the interface? It would be a breaking change, but making sure every handler has the clearMetadata() method seems valid. What do you think?

[paulbalandan]

That seems fair considering that we want to reduce the disconnect of methods in the abstract class and the interface. However, we should also think if other image handlers (if there's any) implementing solely the interface would need the clearMetadata() method. Otherwise, we would be violating the interface segregation principle.

[michalsn]

There are two other possible image handlers that come to my mind: Gmagick and libvips. Both support clearing metadata from images, so including a clearMetadata() method in the interface might make sense.

It's possible that someone has extended the existing handlers to add new features, but this would not produce any problems. If a new handler had been developed, I would assume we’d have seen a PR by now - though perhaps that’s an optimistic assumption.

@samsonasik Do you have any opinion on this one?

[paulbalandan]

Hmm. Then we can go add the clearMetadata method to the interface.

[michalsn]

I have added this new method to the interface.

[datamweb]

LGTM!

[michalsn]

The user guide syntax check seems like the upstream problem: sphinx-doc/sphinx#13533

[michalsn]

Thank you @samsonasik, @paulbalandan and @datamweb