Add workflow for missing TAM/AM for adding customers

Why is this change being made?

Following a lengthy afternoon trying to figure out how to triage http://gitlab.zendesk.com/agent/tickets/168375

We had a user contact us that was not listed as a contact in the Salesforce account. The account did not have a TAM or AM, so there was no verification workflow defined, from a Support or Sales perspective.

This MR adds some basic steps on what needs to be done in this specific situation.

Threads for context:

• https://gitlab.slack.com/archives/C44SXGG8M/p1597205180295500
• https://gitlab.slack.com/archives/C4Y5DRKLK/p1597200878123200

Author Checklist

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• Added a description to this MR explaining the reasons for the proposed change, per [say-why-not-just-what][transparency]
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cc @jgianoutsos / @awinata