Issue Summary

The `wiki/rest/internals/1.0/io/v2/migrations/spaces` endpoint fails to load in 30 seconds for large tenants/spaces. 

Steps to Reproduce

1. Get a sufficiently large tenant with lots of spaces/content. (In the support ticket the space had almost a million attachments.
2. Go to the admin hub and start a sandbox migration.
3. When retrieving the list of spaces, the endpoint times out with the error message "500 Internal Server Error from GET http://atlassian-proxy.mesh:20020/cloudid/16a0d84d-b1a8-46ae-9d18-beb54753917b/confluence/wiki/rest/internals/1.0/io/v2/migrations/spaces"

Expected Results

User should be able to load the list of spaces available for migration

Actual Results

{
    "context": {
    "source": "c2c-middleware-assistant"
    },
    "errorCode": "T1009",
    "errorMessage": "500 Internal Server Error from GET http://atlassian-proxy.mesh:20020/cloudid/16a0d84d-b1a8-46ae-9d18-beb54753917b/confluence/wiki/rest/internals/1.0/io/v2/migrations/spaces"
}

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available