Create a solution to support the ordering of custom fields.
Main features:

• the ordering sequence should not have duplicates (not like 1,2,2,3)

• the order sequence should not have gaps (not like 1,3,4)

Possible solution:

• update the existing implementation of PUT /custom-fields{id} to disable order update of custom fields

• add an additional endpoint to update a collection (PUT /custom-fields) of custom fields including order update

Use case:
Given we have two custom fields with order #1, #2 accordingly
When user wants to swap a custom field ordering (#1 --> #2, #2 --> #1)
Then user should send the whole collection of custom fields on PUT /custom-fields with changed order.

Use case:
Given we have two custom fields with order #1, #2 accordingly
When user updates one of the custom fields (uses PUT /custom-fields{id} ) with changed order
Then user should receive a message "To change the order for a custom field send the collection to PUT /custom fields" or similar.

Acceptance criteria:

• unit tests