Function: setIssuer(uint256 assetID, address issuer)
This function sets the issuer of the asset.
Inputs
assetIDControl: Fully controlled by the caller.
Constraints: Must be an asset ID.
Impact: Specifies the asset to change the issuer.
issuerControl: Fully controlled by the caller.
Constraints: Must be a nonzero address.
Impact: New issuer of the given asset.
Branches and code coverage
Intended branches
Revoke the issuer role of the old issuer.
Grant the issuer role to the new issuer.
Negative behavior
The caller is the owner.
Given asset ID is valid.
Asset token does not have a pending issuing process.