Linting: validate json variables

[fahad19]

Potential issue

If variables with json type are involved, check if the stringified form of JSON is parsable or not and fail linting if not.

This helps avoid prod issues early.

Where to update?

• featurevisor/packages/core/src/linter/featureSchema.ts

  Line 75 in 7d9cd45

  variables: Joi.object().optional(), // @TODO: make it stricter

• featurevisor/packages/core/src/linter/featureSchema.ts

  Line 88 in 7d9cd45

  variables: Joi.object().optional(), // @TODO: make it stricter

• featurevisor/packages/core/src/linter/featureSchema.ts

  Line 160 in 7d9cd45

  defaultValue: variableValueJoiSchema, // @TODO: make it stricter based on `type`