Fix WeWork API request classification

[jeromewir]

Summary

• send the browser request context expected by WeWork for property, location, and booking API calls
• classify upstream 429 responses as rate limits instead of internal server errors
• return HTTP 429 for rate-limited single and batch booking requests

Investigation

• a location cache miss makes two WeWork API calls: property lookup, then location details lookup
• the batch size does not multiply location lookups
• the location endpoint returned 429 with Resty's default server headers and 200 with authenticated browser headers
• the current Workspace listing endpoint returns 403 for this On Demand account and is not a compatible replacement

Verification

• go test ./...
• go vet ./...
• git diff --check