Remove hardcoded NIDs from IntegrationDocuments

[ademarco]

Scope

NIDs should not be hardcoded, otherwise we will run into this problem:

• We ran operation import on dev
• Content of different type (page) was added to dev
• Migration was rolled back and re-ran with new source content
• Titles of newly imported operations replaced only the title of pages created by the editor

This seems to happen because Operations are imported using their source nid and, when rolling back and importing new operations that have same nid of already existing content, existing content gets overridded, regardless of its type.

Tasks

• Fix this.