Apps in Pixlie AI

[brainless]

As a user, I would like to install "apps" in Pixlie AI that enable be to solve specific problems where I provide access to my data.

Context

As mentioned in #10, we need a model to host apps in Pixlie AI. Apps can set the context for the graph, like:

• Initial problem statement
• The data types that the data extraction should check
• What AI models to use
• Define the stages of text classification, entity extraction, etc.
• Define goals for each stage
• Show output in the admin UI
• Expose output data with API