WIP: Plugin RFC

[hdonnay]

trafficstars

This is the code I wrote in parallel with writing #1032.

This branch has the net-new code added, with the caveat that the URN package needs an expanded test suite and a pass for correctness.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 33.09930% with 667 lines in your changes are missing coverage. Please review.

Project coverage is 53.49%. Comparing base (e8f9aff) to head (e6c8fd4).

Files	Patch %	Lines
internal/cmd/plugintool/mdbook.go	0.00%	243 Missing :warning:
internal/cmd/plugintool/codegen.go	0.00%	123 Missing :warning:
internal/plugin/plugin.go	50.00%	54 Missing and 14 partials :warning:
internal/cmd/plugintool/main.go	0.00%	58 Missing :warning:
toolkit/registry/plugins.go	54.38%	43 Missing and 9 partials :warning:
internal/cmd/plugintool/directive.go	0.00%	49 Missing :warning:
internal/plugin/metrics.go	45.71%	16 Missing and 3 partials :warning:
indexer/ecosystem_loader.go	55.00%	14 Missing and 4 partials :warning:
toolkit/urn/urn.go	87.32%	5 Missing and 4 partials :warning:
libindex/plugin_init.go	57.14%	3 Missing and 3 partials :warning:
... and 6 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1028      +/-   ##
==========================================
- Coverage   55.76%   53.49%   -2.27%     
==========================================
  Files         265      281      +16     
  Lines       16562    17559     +997     
==========================================
+ Hits         9236     9394     +158     
- Misses       6365     7190     +825     
- Partials      961      975      +14     

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.