When choosing an SLO group to assign an SLO to, the input is a text input, not a dropdown

[danifitz]

Description

SLO Group should be a drop down allowing you to pick from existing SLO groups (or create a new one - which leads to a text input). Simply having a text input at the moment leads to user error creating multiple SLO groups by accident for example

My SLO Group my slo group My SLP Group

Steps to Reproduce

Create a new SLO, add it to a group - see SLO group is a text input, not a dropdown.

Expected Behaviour

SLO group is a dropdown which shows existing SLO groups. If you want to create a new SLO group or none have been created, simply offer an option in the dropdown to 'create new SLO group' which then exposes a text input.

Relevant Logs / Console output

N/A

Your Environment

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Additional context

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