Add support for importing Python helper functions into Jinja2 templates

[Copilot]

• Explore repository structure and understand the codebase
• Run existing tests to verify current state
• Design solution for importing helper Python scripts into Jinja2 templates
• Implement changes to TemplateBase to support custom functions via vars parameter
• Add comprehensive tests for the new functionality
• Update docstrings for QueryTemplateTransformation and TemplateFinalizer
• Verify all tests pass (29 tests passing)
• Run full test suite
• Request code review
• Address review feedback:
  • Removed vendor-specific Splunk RBA test
  • Removed redundant risk mapping test
  • Deleted splunk_rba_helpers.py test file
  • Simplified template_vars.py by removing format_price and get_risk_mapping functions
  • Updated all tests to use parse_json for simpler test cases

Summary

Successfully implemented support for importing Python helper scripts into Jinja2 templates. The implementation:

• Adds a new vars parameter to TemplateBase
• Loads functions/variables from a vars dictionary in the Python file
• Makes them available as Jinja2 template globals
• Works with both QueryTemplateTransformation and TemplateFinalizer
• Supports YAML pipeline configurations
• Includes comprehensive error handling
• Fully tested with simplified, vendor-neutral examples

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add support for importing helper Python scripts into post processing</issue_title>
<issue_description>Jinja is a limited template language and I'm quickly approaching the edges of what is possible or what is reasonable code to write.

I am currently writing a template to support Risk Based Alerting in Splunk ES8 and I am assigning risk_object and risk_category based on the logsource of the rule. I would also like to be able to access these mappings in a linter to validate that the rule I am transforming has the correct fields present at PR time so my hope is to have a json file similar to logsources.json that i can reference.

Unfortunately using a json file in Jinja2 to make a scalable solution here is possible but ugly. Jinja only wants to accept imported files as string objects and doesn't have native functionality for parsing things like a json object... so I do some ugly splitting and parsing that would otherwise be trivial in Python.

If I had access to some python files from the jinja template I could do something like this example from SO:

@app.context_processor
def utility_processor():
    def format_price(amount, currency=u'€'):
        return u'{0:.2f}{1}'.format(amount, currency)
    return dict(format_price=format_price)

The above when used like so:

{{ format_price(0.33) }}

Which outputs the input price with the currency symbol

So in my case I could use this to parse the JSON and return the exact fields I want into the jinja template if I were able to define the python file I want to include in the postprocessing template.
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add support for importing helper Python scripts into post processing #379

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