[`update-claims-features`] Fix the process removing new claim fields

[juanjosevazquezgil]

Motivation

Currently, when using this module the process removes any fields not found in the Claim struct. This worked for a while but we don't want to have to update the struct each time a change is made to the claim structure and with more Go experience under our belt it should be possible to allow arbitrary claim structures to be passed and updated, so long as they have a features section.

• vars sections mustn't be removed
• secrets section mustn't be removed

Team acceptance

• The module now processes any kind of Claim without removing any fields, but still updates the features

[juanjosevazquezgil]

After reviewing this issue with the team, rather than allowing arbitrary CRs, the best solution would be create structs based on our JSON Schemas, as we use them to define the claim structure in firestartr