Attributes macro not omitting `None` or lowering booleans

[colinrotherham]

Describe the bug
The macro govukAttributes() does not handle Python specific None, True and False values

To Reproduce
Notice how None appears in the output and booleans are not lowercased:

<div {{- govukAttributes({
  "a": undefined,
  "b": null,
  "c": None,
  "d": "",
  "e": 0,
  "f": False
}) }}></div>

- <div a="" b="" c="" d="" e="0" f="false"></div>
+ <div a="" b="" c="None" d="" e="0" f="False"></div>

Expected behavior

• None values should be output "" (same as null, undefined)
• True and False should be lowercased

Additional context
See our NHS fixes if helpful in NHSDigital/nhsuk-frontend-jinja@2a1938e

[colinrotherham]

I've checked over on GOV.UK Frontend and they're still affected by double escaping too:

<div {{- govukAttributes({
  "data-text": "Testing",
  "data-unsafe-text": "Testing & more",
  "data-safe-text": "Testing &amp; more" | safe,
  "data-escaped-text": "Testing & more" | escape,
  "data-double-escaped-text": "Testing &amp; more" | escape
}) }}></div>

If you'd like to compare alphagov/govuk-frontend#6351 with NHSDigital/nhsuk-frontend-jinja@2a1938e as Jinja was a little less happy to deal with undefined so you might not need all these defensive checks anymore:

- {{- govukAttributes(params.formGroup.attributes if params.formGroup) }}>
+ {{- govukAttributes(params.formGroup.attributes) }}>

[matthew-shaw]

@colinrotherham Interestingly enough, if I apply your changes to the NHS equivalent to the govukAttributes macro I get a single test failure on the Input component where it was expecting a zero (int) value, but was actually omitted. Do you experience the same?

[colinrotherham]

Not that I can see, I've got a test with 0 added here:

https://github.com/NHSDigital/nhsuk-frontend-jinja/blob/2a1938e1d2d5df38b180ff5b3bc3c11f25543447/tests/test_attributes_macro.py#L91-L106