Explicitly set iat claim of token

[iamacook]

Summary

This allows for explicit setting of the iat (Issued At) JWT claim. This allows us to set the issuedAt value of a SIWE message as the iat of the JWT token. Before, the package used for token generation would use "now".

In order to achieve the above, this adds a new issuedAt option to the JwtService['sign'] method, refactoring the jwtClientFactory to isolate connection logic between jsonwebtoken and our JwtService. The niches of the package, e.g. setting the iat inside the payload, not the options now happen in the factory.

Changes

• Refactor jwtClientFactory to return a "standardised" client.
• Add an issuesAt option to the JwtService['sign'] method.
• Add/update associated test coverage.

[coveralls]

Pull Request Test Coverage Report for Build 8723040148

Details

• 11 of 11 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.05%) to 93.084%

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Totals
Change from base Build 8722902980:	-0.05%
Covered Lines:	6810
Relevant Lines:	7062

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💛 - Coveralls