Feat/custom app

[cachho]

Description

I have basically rewritten the whole app.

1. Added custom app
2. Shared code between apps
3. Improved open source app (takes config now)
4. Error handling
5. documentation update

Todo:

docs: add providers
docs: add separate custom config for the different App configs.

This itself shouldn't really be breaking, the breaking changes were already accepted in #305

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• Documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Unit tests
• Manual tests (example in docs /advanced/app_types#customapp)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

Maintainer Checklist

• closes #xxxx (Replace xxxx with the GitHub issue number)
• Made sure Checks passed

[cachho]

Not sure what's wrong with the tests.