define get_search_results to fix autocomplete search errors

[EricOuma]

Resolves #67

Proposed changes

The AutoCompleteView uses get_search_results at some point with uses get_search_fields. Because some of the search fields defined are for typesense and not the model, an error occurred when the Django ORM tried to use such fields.
This PR overrides the get_search_results method so that it can be used in a typesense safe way.

Types of changes

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• Bugfix (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)
• Documentation Update (if none of the other choices apply)

Checklist

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• I have read the CONTRIBUTING doc
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

[KengoWada]

@EricOuma code LGTM.