[RFC] Proposal: Decompose super-components

[susnux]

• From: Last call for @nextcloud/vue v9 breaking changes #6384
• Reported by: @ShGKme

Proposal: decompose "super" components.

A super-component is a large component that tries to do too much work for different, sometimes very narrow, cases.

Why

Such components often have tens of props, complex implementation and 1000-2000+ lines of code, while 200-400 is a limit for a good component.

Examples

• NcActions, covers:
  • Simple menus, including navigation and inline feature
  • Custom menus with custom button contents
  • Dialogs with forms
• NcAvatar
  • Minimal: just an image
  • Maximum: user metadata fetching + user status + contacts menu
• NcAppSidebar
  • On one hand - a universal sidebar
  • On another - contents Files-specific app features such as "favorite"
  • Same with NcModal with viewer-only features
• NcSelect
  • Universal component, but has UserSelect as built-in feature
  • ✅ was already decomposed in v9 with feat!: split NcSelect super component into NcSelect and NcSelectUsers #6732

What to do

• Decompose to base components and more specific components
  • e.g. NcSelect => NcSelect + NcSelectUsers
• Make a base component extendable and customize in place where needed
  • e.g. NcAppSidebar for Files app use cases