No SPDX License Identifier

[dindonero]

There's no SPDX-License-Identifier in any of the contracts, so solc compiler will always throw that warning when I import your contracts. Is it supposed to be like this? Thanks

[gtala]

Same as @dindonero ,SPDX license is missing in the v2-core contracts, so we get warnings messages every time we compile our contracts solution

[saman-pasha]

Please add SPDX license line, all the time i got these warnings.
i think interfaces of v2-core and v2-periphery is enough