Fix kwargs replacement bug in template function formatting

[Copilot]

The formatter was potentially replacing **kwargs syntax with {} in Jinja2 template function calls due to unsafe evaluation of function parameters.

Problem

When formatting templates like:

{% macro link_button(text, href='') %}
    {{ button(text, type="link", _="on click go to url '"~href~"'", **kwargs) }}
{% endmacro %}

The **kwargs could be replaced with {}, breaking the template functionality.

Root Cause

The format_data function in src/djlint/formatter/indent.py attempts to evaluate template function parameters using eval() as a fallback when JSON parsing fails. While **kwargs syntax normally fails eval and should preserve the original content, there were edge cases where this could interfere with Python unpacking syntax.

Solution

Added a defensive check to prevent eval() from being called on any content containing ** syntax:

# Before (risky):
evaluated = str(eval(contents)) if contents != "object" else contents

# After (safe):  
if contents != "object" and "**" not in contents:
    evaluated = str(eval(contents))
    # ... existing unwrap logic
else:
    contents = contents.strip()  # Preserve original content

This ensures that **kwargs, **data, and any other Python unpacking syntax is always preserved in template function calls.

Changes

• Modified format_data function to skip evaluation for content containing ** syntax
• Added comprehensive test cases covering various **kwargs scenarios
• Preserved all existing functionality for content without ** syntax

The fix is minimal and surgical - it only affects the specific eval logic path that could cause issues, while maintaining all other formatter functionality.

Fixes #1030.

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