Refactor `method` in `GlobalConstraintInterface` to be an enum.

[tsuberim]

Reading the code, I saw that the _method parameter in here is always called with one of the following:

• mintReputation
• mintTokens
• registerScheme
• unregisterScheme
• sendEther
• externalTokenTransfer
• externalTokenTransferFrom
• externalTokenIncreaseApproval
• externalTokenDecreaseApproval
• genericAction - all other actions.

Can we refactor it to use an enum instead?

[leviadam]

The reason this is so was to leave the possibility for future upgrades.
But I think we can still make it better than it is.

[tsuberim]

Enums are implemented in solidity as uint. So you could easily add more without breaking anything (as long as you don't remove previous ones and keep them in the same order). Using enums, you get a compilation error if you use an undefined method type.

[orenyodfat]

@dev-matan-tsuberi can you check if that indeed save gas ?

[tsuberim]

@orenyodfat didn't say it saves gas (though it may)

[orenyodfat]

@dev-matan-tsuberi if it is, i guess it worth implement that..otherwise I am not sure.

[tsuberim]

@orenyodfat I don't think there's a difference because they are both bytes32 underneath.

[orenyodfat]

Could you confirm that ?