Editor: Make mime type config less confusing

Task Description

We currently pass this list of mime/file types to the editor:

https://github.com/GoogleForCreators/web-stories-wp/blob/f130e0cfa2c69ddd07201db7c1b74d58b24bf341/includes/Admin/Editor.php#L363-L369

As we are working on some documentation on using the decoupled story editor, it became more obvious how confusing this config is.

• allowedMimeTypes: map of allowed mime types for actual story elements. For example, allowedMimeTypes.image might contain image/svg+xml or something to say that you can drop SVGs on the canvas
• allowedImageMimeTypes : this is used for places in the design/document tab where you can upload images (video poster, story poster, publisher logo). For example, here we would never want to allow uploading SVGs. Hence this separate config.
• allowedAudioMimeTypes: similarly, this is used for when you want to add background audio to a page.

In addition to that, allowedFileTypes is just a simple array of file types so that in the editor we can say “You are only allowed to upload jpeg, png, gif” etc. We can just get rid of this and use getExtensionFromMimeType from the media package instead.

allowedTranscodableMimeTypes is really pointless too, which is why I opened #10591 for that already.

To-do

• Rename allowedMimeTypes to somehting more obvious, like for example allowedElementMimeTypes
• Maybe rename allowedImageMimeTypes and allowedAudioMimeTypes to something more obvious too
• Make allowedFileTypes obsolete by assembling that on-the-fly in the editor instead, using getExtensionFromMimeType

[ayushnirwal]

There might be a problem with passing down mime types and getting an extension array in the case of image/jpeg since both .jpeg and .jpg have the mime-type image/jpeg. if allowedImageMimeTypes is ['image/jpeg'] allowedImageFileTypes would be ['jpeg'] but MediaUpload would accept both jpeg and jpg files.

[swissspidy]

Precisely. That’s what I meant in the ticket description by saying we can make it obsolete.