When creating a budget investment with an unverified manager (for
example, a manager who isn't part of the local census), there's a
request to `Budgets::InvestmentsController#suggest`. Since the manager
isn't verified, suggestions can't be obtained.
There are serveral ways to fix this problem:
* Add a `suggest` action to Management::Budgets::InvestmentsController,
doing the same thing the main `suggest` action does.
* Give unverified users permission to access investment suggestions
* Give managers permission to access investment suggestions
I've chosen the last one because I thought it was simple and only
changed existing behaviour for managers, but any other solution would be
as valid. I haven't added the `phase: "accepting"` condition to keep it
simple, since a read-only action like this one in the management portal
isn't gonna create security risks.
