Improve the management of permissions

[RiccardoM]

Feature description

Currently when handling permissions inside a subspace, we use the same method that is used inside Linux-based systems: permissions are managed using a single uint value which bytes are read individually. Although this system works properly and allows us to store a single uint value per user/group, it has some downsides:

1. permissions need to be sanitized before being stored, to make sure there are no collisions with values that might be added in the future;
2. each time there is a new value to be added, the PermissionEverything needs to be updated accordingly. An example of this can be seen here: two permissions where added (PermissionInteractWithContent and PermissionEditOwnContent) and thus the PermissionEverything had to be updated as well;
3. every time a module needs a permission that's specific for it, we need to update the subspaces module to include that permission as well.

Instead of doing this, I think we can have a better way of managing permissions that allows each module to register their own permissions without having to always modify the subspaces module each time there is a new one.

Implementation proposal

I suggest to create the following code

// Permission contains the details of a permission
type Permission struct {
  // Identifies the module which the permission is related to
  Module string 
  
  // Identifies the unique code of this permission within the module 
  Code uint16
}


// RegisterPermission allows to register the permission having the given code within the 
// provided module inside the list of supported permissions
func RegisterPermission(code uint16, module string) Permission {
  // ...
}

This way we could store a user permissions as follows:

PermissionPrefix | SubspaceID | UserAddress | -> ProtocolBuffer([]Permission)

Then, modules external to the subspaces one can simply register their custom permissions just like this:

var (
  PermissionCreateContent = subspacestypes.RegisterPermission(1, types.ModuleName)
  PermissionEditContent   = subspacestypes.RegisterPermission(2, types.ModuleName)
)

And use them as follows:

k.HasPermission(ctx, userAddress, 1, PermissionCreateContent)

Please let me know what you think about this. I will write an ADR if you think this change should be implemented @bragaz @dadamu

[leobragaz]

This is a smart approach as it will allows to upgrade the permissions easily and require an on-chain upgrade each time the subspaces module is edited.