How to give an app access to a specific folder in Photos on iPhone?

I installed instagram on my iphone for publishing photo's. Since these apps are known to pull everything from your phone, I thought i would be handy to use a folder for that.

So, I want to give limited access to my photos for an app based on a folder, not individual pictures. This way I can easily see what photo's are allowed for use by the apps (I named the folder '4public'). While anything in there is easily managed from the photo app.

If this is already possible, please tell me how. If not pls click the 'me too' button :)

Thanks for listening.

G.

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