fix EligibleAt null / NewNullTime

[metachris]

📝 Summary

Fixes #470

NewNullTime would always return a valid time, even if the input is null time. This is fixed in this PR.

Changes to DB: if non-eligible block builder submissions are saved, before it would store a valid time for eligible_at and now it will store null in the database. This is the only field affected.

Code:

• mev-boost-relay/services/api/service.go

  Line 2043 in ff1234b

  submissionEntry, err := api.db.SaveBuilderBlockSubmission(payload, simResult.requestErr, simResult.validationErr, receivedAt, eligibleAt, simResult.wasSimulated, savePayloadToDatabase, pf, simResult.optimisticSubmission)

• mev-boost-relay/database/database.go

  Lines 210 to 211 in ff1234b

  	EligibleAt: NewNullTime(eligibleAt),
  	ExecutionPayloadID: NewNullInt64(execPayloadEntry.ID),

TODO?

• add a migration to fix the existing data? It's a lot of data and would probably take quite long to run, so maybe not

---

✅ I have run these commands

• make lint
• make test-race
• go mod tidy
• I have seen and agree to CONTRIBUTING.md

[codecov-commenter]

Codecov Report

Merging #471 (5c2ff74) into main (fab68c4) will not change coverage.
The diff coverage is 100.00%.

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@@           Coverage Diff           @@
##             main     #471   +/-   ##
=======================================
  Coverage   30.86%   30.86%           
=======================================
  Files          24       24           
  Lines        4736     4736           
=======================================
  Hits         1462     1462           
  Misses       3076     3076           
  Partials      198      198           

Flag	Coverage Δ
unittests	30.86% <100.00%> (ø)

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Impacted Files	Coverage Δ
database/types.go	27.27% <100.00%> (ø)