Update django-ucam-apigatewayauth to support Django 5.x

As a developer, 
I want django-ucam-apigatewayauth to support Django 5 
so that new Django 5-based APIs (e.g. identifiers-api) can integrate 
with API Gateway authentication without dependency conflicts.

Background

The current django-ucam-apigatewayauth release (0.0.7) pins Django to >=3.2.7,<4.3.0, which prevents installation alongside Django 5 (>=5.2.7,<6.0.0) used by identifiers-api. Renovate MR !31 (closed) proposes updating Django, but the package's supported Django version range needs to be updated (see !31 (comment 1258803)).

Acceptance Criteria

• The supported Django version range in django-ucam-apigatewayauth is updated to include Django 5.x.