AWS R53 extension update

[katmlee2]

Describe the bug
When using the AWS R53 extension and I want to update the attached load balancer, the new load balancer it references is not saved.

To Reproduce
Steps to reproduce the behavior:

1. Go to a project (that is using load balancer & R53)
2. Click on 'extensions'
3. Delete 'load balancer' extension
4. Add a new 'load balancer'
5. Click on 'R53 extension'
6. Try updating referenced 'load balancer'
7. Can't update

Expected behavior
I expect that I'm able to update the R53 extension with the load balance I specify.

Desktop (please complete the following information):

• Browser [Chrome]

Additional context
Fixed this by deleting and re-adding; however, it's really hard to know the dependency. Maybe some error messaging would be helpful here?