Allow creating wait tokens with custom id

When creating wait tokens it would be helpful if we can pass our own id. This would make some flows easier where it is difficult to store and use the returned token.

The current solution is to set a tag and use the listTokens api to fetch tokens with a specific tag. With this feature we could create a token with id ‘lead-validation:[id]’, wait for it and complete the token some other place where this lead-ID is available without the need to store a random token.

The create token api should return an error when a token is created using the same id without idempotencyKey.