feat(modify): Allow creating fields

[sandrina-p]

Follow-up of #71, scoped on allowing to add new fields

Linear issue (internal)

New specs

Imagine the schema with 2 fields:

const baseSchema = {
  properties: {
    age: {
      title: 'Age',
      type: 'integer',
    },
    family_name: {
      title: 'Family Name',
      type: 'string',
    }
  },
  'x-jsf-order': ['age', 'family_name'],
};

If you want to add a new field to the JSON Schema pass the following config:

const { schema }  = modify(baseSchema, {
  create: {
    username: {
      title: 'Username',
      type: 'string',
    },
  }
)

Which will return the schema:

{
  properties: {
    age: {
      title: 'Age',
      type: 'integer',
    },
    family_name: {
      title: 'Family Name',
      type: 'string',
    },
    username: {
      title: 'Username',
      type: 'string',
    }
  },
  'x-jsf-order': ['age', 'family_name'],
};

Creating an existing field

If you try to create a field that already exists, it get's ignored and it returns a warning.

Here's an example with the age field based on the baseSchema above.

const { schema, warnings } = modify(baseSchema, {
   create: {
     age: { title: "Your age" }
  }
})

console.log(warnings):

[{
  type: "FIELD_TO_CREATE_EXISTS",
  message: `Creating field "age" was ignored because it already exists.`,
}];

Check tests for more examples.

Other features:

• Support adding nested fields
• It supports reordering new fields (check tests and MR feat(modify): Allow customize fields order #78)