Make items.text_id unique

[smadbe]

Motivations

The text_id of items is used as "identifier" internal to tasks themselves. It can be used for tasks to request to navigate to another tasks (tasks do not know the id of the platform but may know the text_id of another task)

Subtasks

• On existing data:
  • set text_id to null when it is just a empty string
  • if several items have the same text_id append "2", "3", "4" to duplicates (1 occurrence in former prod copy)
• Add a unique index on text_id(the index will be soon used for querying)
• Update the create and update item service doc to inform about the constraint
• On create and update item services: there should be a way for the caller (frontend) to know that an error is a problem of text_id uniqueness. -> extract the info from the sql error and pass the info in 403 response