Customizable base page model

[thibaudcolas]

Introduce an overridable AbstractPage class to allow base page fields to be customized per-project.

Intended outcome

• Allow projects to customize base page fields without creating custom views
• Support extensibility for bespoke page model needs
• Reduce need for workarounds when projects need different base page fields

More information

• Per-project base page models #836
• RFC 53: Swappable Page Model
• Feature request: Swappability of main models #11381