Plugin system

[tmpfs]

The plugin design should allow for:

• [ ] Plugin registry (curated initially) see #214
• [x] Support hook as plugins (eg: tailwind)
• [x] Verify plugin version resolution (rev()?) - test bumping and removing lock file!
• [ ] Restore writing lock file for caching
• [x] Plugin versioning and resolution
• [x] Glob patterns to apply plugins to certain pages
• [x] Support plugin namespaces
• [x] Support optional features
• [x] Support defining layouts
• [x] Support adding partials (organized by template engine)
• [x] Support adding asset files (namespaced in /assets/plugins/{plugin-name})
• [x] Support font packs
• [x] Support font pack variants (eg: latin, full etc)
• [x] Support adding stylesheets
• [x] Support adding scripts
• [ ] Support adding pages (std::book can supply standard print template)
• [ ] Support adding files (outside of assets)
• [x] Plugin groups (collections of plugins in a single repo)
• [x] Recursive plugin dependencies
• [x] Add author field to plugin definition
• [x] Support license information (spdx)
• [x] Plugin source URLs (always set for plugins only registry for lock file entries)

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• [x] Migrate built in partials and default layout to plugin
• [x] Migrate feed templates to plugin
• [x] Migrate class-less stylesheets (newcss etc) to plugins
• [x] Migrate search runtime to plugin
• [x] Migrate short codes to plugin
• [x] Migrate the book logic to a plugin (apply layout to pages?)
• [x] Migrate blueprints to use plugins and the plugin registry
• [x] Migrate plugins to use the new automatic computed logic (see #217)

Later we can look at a component system built on top of the plugin system.

[tmpfs]

Initial simple implementations could be:

• [ ] Mathjax
• [x] highlight.js

[tmpfs]

The short code functionality should be migrated to partial plugins.

[tmpfs]

The search runtime and book assets could be migrated to plugins.

[tmpfs]

As of 62f2fc4a68211c3e2f82b9464796003b189392ff the search runtime files are now a plugin and short codes have been migrated to simple partial plugins, see the plugins repo.

[tmpfs]

As of bb90119f66cb1e1eaadd16831476cfe58672e265 the builtin templates have been migrated to the std::core plugin and the feed templates to std::feed.

[tmpfs]

Optional features support integrated in 1898fa3448a7e250271d654a2e83b45e91c28e9e.

[tmpfs]

Consider using non-namespaced dependencies as private modules. So, for example in the case of a font pack we might want a variant but in order to mesh with the feature flags it needs to be a plugin. However publishing another plugin for a private module would be too much maintenance.

If we have the plugin font::inter then it could declare a private local dependency without the namespace of perhaps with a trailing delimiter or keyword either self::regular or just ::regular could resolve to a relative folder regular containing the plugin.

[tmpfs]

Draft scoped plugin support was completed in 1db1caa0c90f2b0cd3894d0eb695c3307c151f4a which allows us to use feature flags to embed specific scoped plugins, used the font::inter package intergrated with the main project website.