Update modifiers to call public view functions

[come-maiz]

Fixes #1179.
Requires #1268, #1269, #1270.

🚀 Description

It should be possible to query the condition that modifiers require.

• 📘 I've reviewed the OpenZeppelin Contributor Guidelines
• ✅ I've added tests where applicable to test my new functionality.
• 📖 I've made sure that my contracts are well-documented.
• 🎨 I've run the JS/Solidity linters and fixed any issues (npm run lint:all:fix).

[frangio]

This is good. Have you looked at the other modifiers in the codebase?

[frangio]

We can remove this Solium annotation because we moved the expression to a function.

[come-maiz]

Removed.

[come-maiz]

@frangio yes, I've checked them all.
The first thing I noticed is that we don't have as many as I though.
And the second is that this is the most common pattern:

  modifier onlyRole(string _role)                                                                                                                                            
  {                                                                                                                                                                          
    checkRole(msg.sender, _role);                                                                                                                                            
    _;                                                                                                                                                                       
  }   

I think I would like to remove of all the check functions. Call the require(hasRole) directly on the modifiers. But this is different from what we discussed, and needs more thought.

[frangio]

Is there an example of that pattern outside of roles? Those have been removed as part of @nventuro's work on roles.

[frangio]

Rebased on master.

[nventuro]

Yup, from what I recall check was only present in Roles, and I removed it for the reasons described above.

[frangio]

LGTM.

[frangio]

Thanks @ElOpio!