Add missing functionalities (identity, slot) + additional tests

[roks0n]

Proposed changes

Added missing functionalities

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (improve a current implementation without adding a new feature or fixing a bug)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Build (changes that affect the build system)
• Docs (documentation only changes)
• Test (adding missing tests or fixing existing tests)
• Other... Please describe:

Checklist

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• I have read the CONTRIBUTING documentation
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

None

[codecov-io]

Codecov Report

Merging #26 into develop will increase coverage by 0.55%.
The diff coverage is 90.62%.

@@             Coverage Diff             @@
##           develop      #26      +/-   ##
===========================================
+ Coverage    76.74%   77.29%   +0.55%     
===========================================
  Files           36       37       +1     
  Lines          645      674      +29     
  Branches        58       61       +3     
===========================================
+ Hits           495      521      +26     
  Misses         128      128              
- Partials        22       25       +3

Impacted Files	Coverage Δ
crypto/message.py	82.6% <100%> (ø)	⬆️
crypto/slot.py	100% <100%> (ø)	⬆️
crypto/identity/keys.py	100% <100%> (ø)	⬆️
crypto/identity/address.py	92.85% <87.5%> (-7.15%)	⬇️
crypto/identity/wif.py	90.9% <90.9%> (ø)

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