App manifests for Candella applications/system services

[alicerunsonfedora]

In the roadmap for AliceOS v3.0.0, one of the plans was to add support for an app manifest rather than class attribute overriding:

Create a system that can read app manifest properties from a markup file instead of directly modifying the ASAppRepresentative class, either as a JSON, YML, or TOML file.

It could also be possible to use the documentation strings with reST support like the suggestion here:

It would be neat if the app manifest could be created entirely from the reST docstring (recommended format by PEP 287)

class Foobanizer(ASAppRepresentative):
   """
   Generate random foobanized strings on the fly.

   :bundleName: Foobanizer
   :bundleId: app.aliceos.foobanizer
   :bundleDir: {AS_APPS_DIR}Foobanizer.aosapp/
   :bundleAuthor: AliceOS Developers
   :bundleVersion: 1.0.0
   """

The docstring can be accessed via the __doc__ attribute.

- ProjectAliceDev/aliceos#28

[alicerunsonfedora]

There doesn't appear to be an easy way to parse docstrings in reST format without importing a third-party library, which will complicate the project due to how Ren'Py handles Python package imports.

However, there is a new proposed format with JSON at the moment. Each app using the CAApplication class can use a manifest.json file to define the properties of the app. A current example of this in the current commits is App Manager, which has been converted to a Candella app.

[alicerunsonfedora]

We now have official documentation on this manifest at https://candella.unscriptedvn.dev/03-candella-app/#the-manifest-file