add ticket metric events stream for zendesk

[xyzjust]

Description of change

Currently singer Zendesk tap does not provide a method for "Ticket Metric Events"

• API reference: https://developer.zendesk.com/api-reference/ticketing/tickets/ticket_metric_events/
• Table Documentation: https://developer.zendesk.com/documentation/ticketing/reference-guides/ticket-metric-event-types-reference/

Manual QA steps

• Ran tap-zendesk locally.

Risks

• Very low as no change to code, only adding new functions.

Rollback steps

• revert this branch.

[cmerrick]

Hi @xyzjust, thanks for your contribution!

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[cmerrick]

You did it @xyzjust!

Thank you for signing the Singer Contribution License Agreement.

[alex-px]

Is there any update on this?

[lidalei]

@alex-px Note I created a PR to do the same thing two years ago. No idea why they don't care.