Add support for conditional prompting in bundle init

[shreyas-goenka]

Changes

This PR introduces the skip_prompt_if extension to the jsonschema library. If the inputs provided by the user match the JSON schema then the prompt for that property is skipped.

Right now only constant checks are supported, but if in the future more complicated conditionals are required, this can be extended to support allOf, oneOf, anyOf etc allowing template authors to specify conditionals of arbitary complexity.

Tests

Unit tests and manually.

[shreyas-goenka]

Manual testing example. Note here question two will be skipped if answer to question one is no:

Schema:

{
  "properties": {
    "question_1": {
      "order": 1,
      "type": "string",
      "description": "\nFirst question",
      "default": "yes",
      "enum": ["yes", "no"]
    },
    "question_2": {
      "order": 2,
      "type": "string",
      "default": "a-default-value",
      "description": "\nSecond question. Only visible if you answered 'yes' to the first question.",
      "skip_prompt_if": {
        "properties": {
          "question_1": {
            "const": "no"
          }
        }
      }
    },
    "question_3": {
      "order": 3,
      "type": "string",
      "description": "\nThird question"
    }
  }
}

Prompts:

shreyas.goenka@THW32HFW6T mlops-stack % cli bundle init ~/mlops-stack

First question: yes

Second question. Only visible if you answered 'yes' to the first question. [a-default-value]: 

Third question: ^C
shreyas.goenka@THW32HFW6T mlops-stack % cli bundle init ~/mlops-stack

First question: no

Third question: ^C

[pietern]

Nice work. The extensions are growing and we should be careful adding more.

[shreyas-goenka]

The skipPrompt function still includes value mutation inside it. This is to make unit testing easier.

Expanded the scope of the function to consider execution of default value as a string and skip assigning default value if the property already has a value.

Note: The abstractions here are kind of messy. We need to combine the config and the renderer structs. I'll work on a followup to do so once this is merged.

[andrewnester]

What are valid types for Const? Only strings and integers?

[shreyas-goenka]

Const can be any type, including null or objects according to the JSON schema spec: https://json-schema.org/draft/2020-12/json-schema-validation#name-const

[shreyas-goenka]

For mlops-stacks, we only the capability to validate const strings right now.

[andrewnester]

@shreyas-goenka what if I define the following const, does it work?

"properties": {
        "def": {
            "type": "float",
            "const": 5.1
        }
    }

[shreyas-goenka]

Tried it out. Does not work for float because of precision issues. (5.1 vs 5.099).

Also does not work for integers due to type not being correct (basically const is parsed as a float rather than an int). I can fix it in a followup PR.