TRANSFER_SUMMARY_DIFF_CHANGE is almost always full update:
```
[
{"op":"replace","path":"/downTotal","value":851320719382},
{"op":"replace","path":"/downRate","value":6139},
{"op":"replace","path":"/upTotal","value":1826972572184},
{"op":"replace","path":"/upRate","value":5480521}
]
```
which is generally less efficient than full object (TRANSFER_SUMMARY_FULL_UPDATE):
```
{
"upRate":5430724,
"upTotal":1827320521117,
"downRate":6062,
"downTotal":851321106383
}
```
Unfortunately there are still many people who prefer static config
file. As such, schema validate the configurations to ensure that
the failure happens loud and early when the config.js is broken.
Also enforces that the length of secret must be larger than 30 as
the JWT secret can be brute forced locally without interaction with
the server.
This ensures that we always have proper configurations and avoids
unnecessary and bad defensive programming practices.
Trim21