RUMM-638 Global RUM attributes

[buranmert]

What and why?

Users may want to use common attributes in their RUM events
We should provide them a convenient way to set those attributes

How?

Now users can add, update or remove global attributes in their RUMMonitor instances

rumMonitor.setAttribute(forKey: "some key", value: "some value") // adds an attribute
rumMonitor.setAttribute(forKey: "some key", value: "some other value") // updates the value
rumMonitor.setAttribute(forKey: "some key", value: nil) // removes the key
let globalAttrs = rumMonitor.attributes // returns current global attributes to be added to events

Note: attributes is thread-safe

Review checklist

• Feature or bugfix MUST have appropriate tests (unit, integration)
• Make sure each commit and the PR mention the Issue number or JIRA reference

[ncreated]

Few comments added 👌. Also, before we merge it, let's discuss with the team the precise product requirements for global attributes processing.

[ncreated]

Just fix the variable name thing, then we can merge 👌

[ncreated]

Ref, I created RUMM-691 Add RUMMonitor benchmarks so we can test if there's no performance drop due to this extra thread switch for every public API call.

[buranmert]

i think the cost should be negligible but if we have concerns, we can do that:

protocol RUMCommand {
  var attributes { get set }
  ...
}
class RUMMonitor {
  func process(cmd) {
    queue.async {
      cmd.attributes.merge(globalAttrs)
      appScope.process(cmd)
    }
  }

then we won't need queue.sync to get global attrs
let me know if you need this