Upon upgrade to 5.0, existing Global Logos are lost

Steps to reproduce

1. Create an instance with a global logo on 4.3.x
2. Upgrade to 5.0
3. Observe that the logo has disappeared and needs to be reuploaded

Response from Product Managers

This is not a bug but rather a naming change that came about during the new header implementation. What Confluence previously called the "global logo" was really just a "default space logo" since it could be overridden on a per-space basis. When the new global header came along, it required us to introduce a true global logo that always appears in the header and doesn't change on a per-space basis. Therefore we renamed "global logo" to "default space logo" and introduced a new, true global "site logo" that's consistent with the other products.

Closing this as 'Not a bug'.