Request(plugin-postgres): pg-pool

[markwolff]

Related to #417

Is it applicable for Node or Browser or both
Node.js

Do you expect this plugin to be commonly used (Weekly downloads)

• pg-pool: 800k DLs/week; dependency of pg -- more important!
• pg-cursor: 50k DLs/week

Additional context

For "complete" postgres support, the pg.Pool and pg.Cursor APIs should also be patched. Only pg-pool is a dependency of pg and is directly exposed by pg, so it gets much more usage. Having these as separate plugins would make overall postgres patching more clean and testable (rather than doing internal file patching). They should live in a similar directory so that all could be simultaneously tested as they would be in the wild, e.g pool.query(...) would be using our pg patching for client.query(...). Initial folder structure is below. PTAL! Alternatively, tests requiring both plugins could be put inside pg/ or pg-pool/ and those tests would just be importing in both plugins.

Folder structure proposal # 1

- packages/opentelemetry-plugin-postgres/
- - tests/       # tests requiring both plugins
- - pg/          # tests and implementation for pg module plugin
- - pg-pool/     # tests and implementation for pg-pool module plugin
- - package.json # mock entry point for running tests in tests/

Folder structure proposal # 2

- packages/opentelemetry-plugin-postgres/
- - pg/          # tests and implementation for pg module plugin
- - pg-pool/     # tests and implementation for pg-pool module plugin
                 # and tests which require both plugins