Emit userEmail in workflow-metadata.json generated by tw runs dump

[ejseqera]

Related to #361, it would be helpful to output the userEmail into the workflow-metadata.json file generated by running tw runs dump.

Current behaviour

Running tw runs dump emits a workflow-metadata.json file that will contain the userId but in order to determine who the user is tied to, this id has to be referenced back to the output of tw -o json members list -o <org> to retriever userName and email:

{
  "pipelineId" : 88330947242108,
  "workspaceId" : 162690105070735,
  "workspaceName" : "testing",
  "userId" : 10273,
  "runUrl" : "https://tower.nf/orgs/scidev/workspaces/testing/watch/4TUilc62wiW0Lj"
}

Desired behaviour

The workflow-metadata.json should also include email at the minimum, to more easily identify the user who had kicked off the run without having to run an additional CLI command. For example:

{
  "pipelineId" : 88330947242108,
  "workspaceId" : 162690105070735,
  "workspaceName" : "testing",
  "userId" : 10273,
  "userName": "esha-joshi",
  "email": "esha.joshi@seqera.io",
  "runUrl" : "https://tower.nf/orgs/scidev/workspaces/testing/watch/4TUilc62wiW0Lj"
}

Use Case

Users of the CLI are taking the metadata generated from the tw runs dump command and feeding it into downstream tools/platforms to aggregate statistics for runs, tie runs to their internal LIMS databases, and generate dashboards. Emails serve as a more effective method for associating metadata to users because they typically used for SSO across various platforms, in contrast to usernames that may be ambiguous and vary from one platform to another.