Add a Shared Modifiers Contract

[andreivladbrg]

After reviewing the PR #1022, I realized how many modifiers are declared multiple times.

For example, the givenNotNull modifier is declared 23 times in different files: https://app.warp.dev/block/6GAXDA0EH90tdp6jocyZ20

IMO this is very redundant, so I suggest adding a common Modifiers contract in the shared dir that can be inherited in Integration_Test.

Also, aside from being redundant, this also makes refactoring and making changes to tests more difficult, resulting in higher maintenance costs.

wdyt @sablier-labs/solidity ?

[andreivladbrg]

tagged engineers by mistake, it should have been only solidity 😆

[smol-ninja]

Totally on board with that idea. What do you think about shifting all the modifiers, that are used in at least two files, over to the Modifiers contract?

Like, in the shared folder, we've modifiers scattered across various contracts, and some are even duplicates. For instance, both withdrawMax.t.sol and withdraw.t.sol have the modifier givenEndTimeInFuture. We could just merge them into one, right? And the modifiers that are only used once can be kept in the same test contracts.

[PaulRBerg]

Agree and makes sense to dump all modifiers in one place.