Add instruction to backfill versions table of agent_config when a new field is added in the configuration

Issue: Ensure workspaces_agent_configs for older versi... (#541902 - closed)

What does this MR do and why?

Adds instruction to backfill versions table of agent_config when a new field is added in the configuration. Read the issue for more info.

References

Ensure workspaces_agent_configs for older versi... (#541902 - closed)

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