Conduit: filereader / filewriter plugins and compatibility changes.

[winder]

Summary

• New filereader plugin.
• Small changes / improvements to the filewriter plugin:
  1. Add tags to the BlockData type so that the serialization is explicit.
  2. Change the block encoder function to use go-codec, the StateDelta object contains a map with non-string keys which caused a problem with the json encoder.
  3. Use t.TempDir() for tests so that the tests don't leave artifacts behind.
  4. Save a genesis.json file
  5. Some new configurations - Removing the vote certificate (should be in the filter plugin?), specifying the filename format.

Test Plan

New unit tests.

[codecov[bot]]

Codecov Report

Merging #1253 (eb6631e) into conduit (99a848c) will increase coverage by 0.32%. The diff coverage is 81.04%.

@@             Coverage Diff             @@
##           conduit    #1253      +/-   ##
===========================================
+ Coverage    58.39%   58.72%   +0.32%     
===========================================
  Files           77       78       +1     
  Lines        10332    10463     +131     
===========================================
+ Hits          6033     6144     +111     
- Misses        3772     3786      +14     
- Partials       527      533       +6     

Impacted Files	Coverage Δ
data/block_export_data.go	82.69% <ø> (ø)
importer/helper.go	8.61% <0.00%> (-0.13%)	:arrow_down:
util/ledger_util.go	62.50% <25.00%> (-3.41%)	:arrow_down:
exporters/postgresql/postgresql_exporter.go	80.23% <40.00%> (-2.90%)	:arrow_down:
exporters/filewriter/file_exporter.go	83.33% <82.60%> (+11.59%)	:arrow_up:
util/util.go	76.92% <85.71%> (+10.25%)	:arrow_up:
importers/filereader/filereader.go	85.93% <85.93%> (ø)
importers/algod/algod_importer.go	79.31% <100.00%> (+0.73%)	:arrow_up:
processors/blockprocessor/block_processor.go	64.65% <100.00%> (+0.46%)	:arrow_up:
processors/blockprocessor/initialize.go	63.88% <100.00%> (+0.33%)	:arrow_up:
... and 2 more

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[shiqizng]

LGTM