Show only monitors ids/or URL (without the subject line) in Datadog monitors resource ids

[AmineChikhaoui]

Currently the subject line which is the resource name attribute might be too long to show in the output of nixops info. It might be better to make it only show the monitor id or consider showing the monitor URL that redirects to the Datadog console:

+----------------------+-----------------+--------------------------------+-----------------------------------------------------------------------------------+------------+
| Name                 |      Status     | Type                           | Resource Id                                                                       | IP address |
+----------------------+-----------------+--------------------------------+-----------------------------------------------------------------------------------+------------+
| machine              |  Missing / New  | ec2 [us-east-1]                |                                                                                   |            |
| disk-usage-monitor   | Up / Up-to-date | datadog-monitor                | [minimal-lb] disk space on {{host.name}}:{{device.name}} is under 10% [ 1649279 ] |            |
| fm_exports-monitor   |  Up / Obsolete  | datadog-monitor                | [minimal-lb] fm_exports batch failure [ 1649272 ]                                 |            |
| memory-monitor       | Up / Up-to-date | datadog-monitor                | [minimal-lb] Usable memory in {{host.name}} is under 3Gb [ 1649142 ]              |            |
| no-data-monitor      | Up / Up-to-date | datadog-monitor                | [minimal-lb] {{host.name}} no data is being collected [ 1655463 ]                 |            |
| unit-failure-monitor | Up / Up-to-date | datadog-monitor                | [minimal-lb] {{host.name}} systemd unit failed [ 1639636 ]                        |            |
| weekly_fe-monitor    |  Up / Obsolete  | datadog-monitor                | [minimal-lb] weekly_fe batch failure [ 1649271 ]                                  |            |
| keypair              | Up / Up-to-date | ec2-keypair [us-east-1]        | charon-430fef8c-c897-11e6-9954-3417eb5c4c9c-keypair                               |            |
| sg                   | Up / Up-to-date | ec2-security-group [us-east-1] | charon-430fef8c-c897-11e6-9954-3417eb5c4c9c-sg                                    |            |
+----------------------+-----------------+--------------------------------+-----------------------------------------------------------------------------------+------------+

[AmineChikhaoui]

Improvement in PR #612