NFTMethod.create generates incorrect index

[has5aan]

Expected behavior

NFTMethod.create should use integer value for index segment of NFT ID.

Actual behavior

NFTMethod.create uses string as index segment for NFT ID.

Steps to reproduce

Creating an NFT through mintNft command of testNft module.

Which version(s) does this affect? (Environment, OS, etc...)

feature/6917-implement-nft-module branch.