Envelope signer / crypto abstractions

[vitiko]

for implementing different signing algorithms

[coveralls]

Pull Request Test Coverage Report for Build 9643258919

Details

• 68 of 80 (85.0%) changed or added relevant lines in 3 files are covered.
• 10 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.1%) to 57.143%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
extensions/envelope/signer.go	32	34	94.12%
extensions/envelope/middleware.go	18	21	85.71%
extensions/envelope/crypto.go	18	25	72.0%

Files with Coverage Reduction	New Missed Lines	%
extensions/token/balance_utxo.go	10	69.61%

Totals
Change from base Build 7459099486:	-0.1%
Covered Lines:	3992
Relevant Lines:	6986

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💛 - Coveralls