Add response events for slack

[sean-brydon]

What does this PR do?

Provides some feedback to the user about the actions they have carried out within the create-event modal.

For now this is a simple implementaiton however the error handling can be improved see

Fixes # (issue)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How should this be tested?

• Create an event with slack
• See info being displayed back to the user

[vercel]

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