Cognito attribute for TimeZone creates a custom attribute

[barticus]

Hi,
I've created a user pool with custom schema and have used UserPoolAttribute.TIMEZONE as the attribute name.
This creates an attribute named custom:timezone but i believe it should actually have mapped to the zoneinfo standard attribute.

Reproduction Steps

Create a user pool with a schema like:

const userPool = new cognito.CfnUserPool(this, "UserPool", {
      autoVerifiedAttributes: [cognito.UserPoolAttribute.EMAIL],
      usernameAttributes: [cognito.UserPoolAttribute.EMAIL],
      schema: [{
        name: cognito.UserPoolAttribute.EMAIL,
        attributeDataType: "String",
        required: true,
        mutable: true
      }, {
        name: cognito.UserPoolAttribute.TIMEZONE,
        attributeDataType: "String",
        required: false,
        mutable: true
      }]
});

After creation, inspect the user pool in the console, there will be a "custom:timezone" attribute listed.

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This is 🐛 Bug Report

[barticus]

Link:

aws-cdk/packages/@aws-cdk/aws-cognito/lib/user-pool.ts

Line 107 in 62c2125

TIMEZONE = 'timezone',