Adding post deploy step needed for slack notifications

[dwhitestratiform]

Description

This is a chicken and egg problem. This workflow needs to exist on main before I can test and use it in a development branch. So here I am.

After this is pushed to main I can pull this into my dev branch and actually use it.

Related ticket(s)

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How to test

Push and verify this doesn't break the mcr main deploy ... I tested this in core and it worked.

Notes

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Pre-review checklist

• I have performed a self-review of my code
• I have added thorough tests, if necessary
• I have updated relevant documentation, if necessary

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Pre-merge checklist

Review

• Design: This work has been reviewed and approved by design, if necessary
• Product: This work has been reviewed and approved by product owner, if necessary

Security

If either of the following are true, notify the team's ISSO (Information System Security Officer).

• These changes are significant enough to require an update to the SIA.
• These changes are significant enough to require a penetration test.

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convert to a different template: test → val | val → prod

[dwhitestratiform]

this will never pass PR steps because its a skipci branch ... going to merge and keep an eye on main to make sure it passes.