Automated Discovery of `PackageInstallationPlugin`

[dtdesign]

PIPs are manually registered through the XML-PIP but in practice are very limited. They must be placed in the core’s directory because any app directory is not necessarily available during the installation or uninstallation of a package. Furthermore their name must be unique because they are referenced by their name and not their full path.

This makes them an ideal candidate for an auto discovery by looking for files in the PIP directory:

• Prevents the pitfall of registering it in an app’s directory.
• Ensures uniqueness by more-or-less gracefully handling file collisions.
• Easily cacheable and relatively static, one less table to deal with.