Make CustomDisplayCostAndPrice changeable via ChangeConfiguration.req

[Matthias-NIDEC]

OCPP Version

OCPP1.6

Describe the bug

There is the request to make the CustomDisplayCostAndPrice writable via ChangeConfiguration.req (readonly=false).

In that sense,
"It is good practice to define a boolean configuration key ("CustomDisplayCostAndPrice"), that a Central System
can query to find out if this customization is present and optionally use it to enable or disable the customization:" Chapter 3.1
(OCPP & California Pricing Requirements, 3.1) is realized.

The related datatransfer callbacks have to be deregistered or an answer RebootRequired is possible.

To Reproduce

The variable CustomDisplayCostAndPrice can not be changed from backend site.

Anything else?

No response