[WIP] Added `reason` field, fixes #766.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #766
| License       | MIT
| Doc PR        | ***This would need to be documented but I don't know where.***

**TODO**
- [ ] Is every module upgraded when executing `upgrade.php`?
- [ ] Document this feature anywhere