III-4424 Improve json encoding

[LucWollants]

Added

• Added Json class to have a more consistent way of encoding and decoding to Json

Changed

• Replaced occurrences of json_encode with Json::encode
• Replaced occurrences of json_decode with Json::decode
• Boy scouting on the changed classes

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Ticket: https://jira.uitdatabank.be/browse/III-4424

[bertramakers]

This is one of the most important usages because it determines how the JSON response of searches is encoded. It's interesting then that exactly this encode uses extra options which are not standardized in the Json class. Maybe we should add it as a encodeForHttpResponse() or something like that so it's clear it should be used in that context, and it will always use the right options for http responses then? Also applicable to udb3-silex I think, where we encode JSON for responses, but also for serializing things in our database or queuing messages for example. So it might be good to differentiate between context, like encodeForHttpResponse() and encodeForSerialization() for example?

[LucWollants]

For now I changed the specific case to encodeForHttpResponse, if we get more flavours better naming is indeed needed.

[bertramakers]

Yes in this app that is sufficient. I meant that in udb3-silex it might be good to add different flavors when we replace all usages of json_encode() there. I think right now we always use Json::encode() which just uses THROW_ON_ERROR. But even if it's always the same right now, it might be good to already differentiate a bit based on context so we can easily add options later depending on the context.