Ensure object mappers are configured with ignore unknown for forward compatibility

[CRogers]

Before this PR

Currently, we read json values with object mappers that do not ignore unknown properties. This means it is hard/impossible to add new fields to objects in the recommened-product-dependencies plugin (for example: to mark pdeps as optional in libraries).

After this PR

==COMMIT_MSG==
Ignore unknown properties in serialized data to support forward compatibility.
==COMMIT_MSG==

Possible downsides?

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Type

• Feature
• Improvement
• Fix
• Break
• Deprecation
• Manual task
• Migration

Description

Ignore unknown properties in serialized data to support forward compatibility.

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[CRogers]

I've done these as well as internal repos use these objects with their own object mappers (this will also complicate the rollout of any serialisation change...)

[carterkozak]

Don't we use the client objectmappers which ignore unknowns by default? In some cases we may wish to fail on unknowns (for validation)

[CRogers]

@carterkozak for deserialising these, we do not use client/conjure object mappers. I also can't think of a place we want to fail with new properties - it effectively means we can't change anything?

[carterkozak]

I think the default mapper does what we want, but the cases where we want to validate against unknowns likely aren't worth a risk of failing.
👍

[CRogers]

@carterkozak The default object mapper unfortunately doesn't ignore unknown properties - I sadly know this due to former $internal-product I worked on in pre-conjure times that failed to set ignoreUnknown everywhere, so nothing could ever change.

Here is the a test that verifies that off develop:

Caused by: com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException:
Unrecognized field "something-else" (class com.palantir.gradle.dist.ImmutableRecommendedProductDependencies$Json),
not marked as ignorable (one known property: "recommended-product-dependencies"])

[svc-autorelease]

Released 7.16.0