## Description
This PR adds backwards compatibility for older snowflake datasources so
that we wont need migration.
With new updates on snowflake plugin for key pair authentication, we
have introduced a new field in authentication object called
authenticationType, this field is responsible for telling us whether
it's a basic authentication or key pair authentication. For older
datasources, this field wont be there, so in order to ensure that those
datasource continue to work smoothly, we have added a fallback
mechanism, where if any datasource does not have authentication field,
it will be considered as basic auth and we will set its properties
accordingly. This PR adds that support
### Steps to test:
1. Create a snowflake datasource along with queries on app.appsmith.com
2. Attach these queries to table widget so they run on page load
3. Export this app and get json
4. Import this json on the DP of this PR, the queries should work
Fixes#34627
_or_
Fixes `Issue URL`
> [!WARNING]
> _If no issue exists, please create an issue first, and check with the
maintainers if the issue is valid._
## Automation
/ok-to-test tags="@tag.Datasource"
### 🔍 Cypress test results
<!-- This is an auto-generated comment: Cypress test results -->
> [!TIP]
> 🟢🟢🟢 All cypress tests have passed! 🎉🎉🎉
> Workflow run:
<https://github.com/appsmithorg/appsmith/actions/runs/9759249212>
> Commit: f68972710918b450d989c1d28a9286a397fc08bd
> <a
href="https://internal.appsmith.com/app/cypress-dashboard/rundetails-65890b3c81d7400d08fa9ee5?branch=master&workflowId=9759249212&attempt=1"
target="_blank">Cypress dashboard</a>.
> Tags: `@tag.Datasource`
<!-- end of auto-generated comment: Cypress test results -->
## Communication
Should the DevRel and Marketing teams inform users about this change?
- [ ] Yes
- [ ] No
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
- **Bug Fixes**
- Enhanced backward compatibility for Snowflake plugins by handling
cases where `authenticationType` is not present in older datasources.
- **New Features**
- Improved datasource configuration by cleaning the authentication
object in the `DatasourcesApi`.
- **Refactor**
- Simplified authentication type handling by removing unused
`USERNAME_PASSWORD` and `KEY_PAIR` enums in `DBAuth`.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
---------
Co-authored-by: “sneha122” <“sneha@appsmith.com”>
19623ddd7a