Fix BigDecimal output in sum filter

[adamklingbaum]

• Closes Summing floats with the sum filter #1725
• Replaces Don't render sum filter results in scientific notation. #1728

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Thank you, @jg-rp, for identifying this bug and helping to implement the fix.

Summary

This PR addresses a bug in the sum filter when handling arrays containing floats and thus yield a result that is a float.

Previously, the sum filter would return a BigDecimal, which would render in scientific notation, when summing floats. This behaviour was inconsistent with other math filters.

The change in this PR ensures that the sum filter returns a float instead of a BigDecimal when summing floats, aligning its behaviour with other math filters.

For example:

liquid/lib/liquid/standardfilters.rb

Lines 908 to 911 in 0b93182

	def apply_operation(input, operand, operation)
	result = Utils.to_number(input).send(operation, Utils.to_number(operand))
	result.is_a?(BigDecimal) ? result.to_f : result
	end

Changes

• Updated the sum filter in lib/liquid/standardfilters.rb to convert BigDecimal results to floats when summing floats.
• Added tests in test/integration/standard_filter_test.rb to verify the correct behaviour of the sum filter when handling floats.