Make use of permission_handler instead of our own implementation

[TheLastGimbus]

This PR adds permission_handler as a dependency, and makes use of it. Thanks to this, we will have easier job of messing with permissions, and we can check permissions without Activity (see discussion in #287 )

Changes made by me still need to be tested on iOS, and on new Android 11 !

If @CaiJingLong will decide to accept this, it will also be nice to remove old attempts in Android and iOS sides.

[CaiJingLong]

This PR will not be merged, because referencing other flutter libraries will cause version conflicts.

[TheLastGimbus]

Not necessary

When you write library: ^2.0.0, pub will accept anything 2.*.*

So user can have ^2.4.3, other library can have ^2.0.1, and everything will work

[CaiJingLong]

No, for example, if the plugin you posted is updated to 3.0, plugin 1 depends on 3.0, and plugin 2 depends on 2.0.
When they are used by the same person, they conflict.

---

The library part of this plugin will not depend on other plugins, nor will it in the future

[TheLastGimbus]

So what can we do? I really need the library to work in the background - can we just check how permission_handler implemented it, and copy-paste the same in here?

[CaiJingLong]

I think what you need may be to ignore the permission check, the default must have permissions, and the contentResolver must be available.

[CaiJingLong]

I can add an option to support this, but correspondingly, the risk needs to be borne by the user of plugin.

[TheLastGimbus]

I can implement everything what is needed to run this plugin in the background - just tell me what needs to be done

[CaiJingLong]

I push a change to ignore permission check.
You can try to use 0.6.0-dev.3 version in your project.
And, you can try to use permission_handler to handle permission.

Next code to ignore permission check.

await PhotoManager.setIgnorePermissionCheck(true);

Then you need to make sure that the permissions are available before calling the method.