Config: Cannot create new version for legacy configs missing completion.type

[vprashrex]

Describe the bug

Legacy configurations in the database do not have the completion.type field.
When updating such configs with a valid type (e.g., "text"), the backend throws an error:

Cannot change config type from 'None' to 'text'. Type is immutable.

To Reproduce

Steps to reproduce the behavior:
For this config_id: c56df7c0-85cf-4d78-9309-9616688f36a8
(This config was created before completion.type became mandatory and does not contain the type field.)

1. Create a new version for the above config_id
2. Provide a valid completion configuration with a mandatory type, for example:

{
  "config_blob": {
    "completion": {
      "provider":"openai",
      "type": "text",
      "params": {
        "model": "gpt-4o-mini",
        "temperature": 1,
        "instructions": ""
      }
    }
  },
  "commit_message": ""
}

4. Submit the request
5. See error

Expected behavior
The system should allow creating a new version for legacy configurations where completion.type is missing.

Screenshots

Additional context
Options to fix

1. Database Migration

• Update all existing records where completion.type is missing → set default "text".

2. Backend Server to Support for None

[kartpop]

@Prajna1999 should we fix this too before others run into this issue while integrating