Load simulator

[aatkin]

Initial version of load simulator. Run concurrent headless chrome instances against target REMS. CLI accepts following optional arguments:

• --url - which url to run against (default: http://localhost:3000/)
• --concurrency - how many threads to start (default: 8)

Quick start:

• start REMS server (e.g. from CLI: lein run)
• start separate simulator REMS from CLI: lein run load-simulator [--url url] [--concurrency n] (no args uses default values)

Checklist for author

Remove items that aren't applicable, check items that are done.

Documentation

• [ ] Update changelog if necessary
• [ ] Update docs/ (if applicable) -- might be good idea to document?
• [ ] ADR for major architectural decisions or experiments -- might be good idea to document?

Testing

• [ ] Complex logic is unit tested -- what would be appropriate to test here?
• [ ] Valuable features are integration / browser / acceptance tested automatically -- what would be appropriate to test here?

Follow-up

• [ ] New tasks are created for pending or remaining tasks