go/worker/registration: Clean dead registration signer code

[martintomazic]

Motivation: Simplify #6474 (comment).

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🔨 Latest commit	573fb3c
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[codecov]

Codecov Report

❌ Patch coverage is 78.12500% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.01%. Comparing base (fcf368b) to head (573fb3c).
⚠️ Report is 12 commits behind head on master.

Files with missing lines	Patch %	Lines
go/oasis-node/cmd/node/node.go	58.33%	5 Missing and 5 partials ⚠️
go/worker/registration/config/config.go	71.42%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6481      +/-   ##
==========================================
- Coverage   64.45%   64.01%   -0.44%     
==========================================
  Files         699      698       -1     
  Lines       68216    68195      -21     
==========================================
- Hits        43966    43653     -313     
- Misses      19187    19521     +334     
+ Partials     5063     5021      -42     

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[peternose]

Nice 😉

[peternose]

This is not the best, as looking at the constructor signature one has no idea that this can be nil. Can we add another commit and fix TODO below (stop abusing no-op workers)?

[martintomazic]

This is not the best, as looking at the constructor signature one has no idea that this can be nil

Go type system is explicit. The current constructor signature means: entity id may be nil or have value of type public key. Pointer types are not so nice workaround for the missing option type in go. You use them to avoid copying huge values, have a shared reference, or mimic optional type.

What is not best is to assume that a pointer is not nil unless documented explicitly. We do this too often, with immutable small structs (smell), that should not be passed as pointers in the first place.

I agree this is still ugly, thus I have added an explicit comment. Clean way is to get rid of no-op workers but this is not trivial.