feat(ui): Make CaraML AI placeholder app generic

[deadlycoconuts]

Context

This PR is a follow up from #109, which makes the CaraML AI placeholder app generic enough to support all forms of apps that need to be rendered as a page with an embedded Streamlit app by the MLP UI. It also consolidates all the configuration needed to render this page into a single location (the Applications.PlaceholderPageConfig struct).

Essentially, while the CaraML AI placeholder app was previously hardcoded into existence in the MLP server/UI through various fragmented pieces like the CaramlAIStreamlitHomepage config or the hardcoded CaraMLAIPage.js page's title, setting up new streamlit placeholder apps now simply requires specifying these in the Applications config file that is read by the MLP server:

mlp:
  config:
    applications:
      # ...
      - name: CaraML AI
        description: Gateway for accessing LLM models
        homepage: /caraml-ai
        isProjectAgnostic: true
        configuration:
          iconName: timelionApp
        placeholderPageConfig:
          URL: https://30days.streamlit.app?embed=true
      - name: Dummy App
        description: Dummy app for testing MLP-hosted streamlit apps
        homepage: /dummy-app
        isProjectAgnostic: true
        configuration:
          iconName: canvasApp
        placeholderPageConfig:
          streamlitURL: https://8days.streamlit.app?embed=true

Changes

Fundamentally, the changes to this PR are relatively straightforward, we simply remove the hardcoded streamlit app and conditionally generate React routes only after the list of apps have been retrieved from the v2/applications endpoint on the MLP API server. The React AppRoutes are also made to intentionally not render until that happens (this is because React routes are rendered synchronously, meaning we can't add routes on-the-fly without re-rendering all the routes again).

The isLoaded context value has also been added to ApplicationsContext as a useful flag to determine when the response from the applications endpoint has been returned.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 57.14%. Comparing base (09c363a) to head (ccc92d6).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #110   +/-   ##
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  Coverage   57.14%   57.14%           
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  Files          47       47           
  Lines        2443     2443           
=======================================
  Hits         1396     1396           
  Misses        851      851           
  Partials      196      196           

Flag	Coverage Δ
api-test	57.14% <ø> (ø)

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[leonlnj]

LGTM

[deadlycoconuts]

Thanks for the quick review and the comments everyone! Merging this now! 🙏🏼