Add BeJsonSerializable extensions for objects

[vbreuss]

Background and motivation

As discussed in #2205 we want support for System.Text.Json. I would suggest to keep it as similar as possible to the existing extension package FluentAssertions.Json.

API Proposal

Add the following methods for ObjectAssertions (similar to ObjectAssertionsExtensions in FluentAssertions.Json):

    public AndConstraint<TAssertions> BeJsonSerializable(string because = "", params object[] becauseArgs);
    public AndConstraint<TAssertions> BeJsonSerializable<T>(string because = "", params object[] becauseArgs);
    public AndConstraint<TAssertions> BeJsonSerializable<T>(Func<EquivalencyOptions<T>, EquivalencyOptions<T>> options, string because = "", params object[] becauseArgs)

These methods should assert that an object can be serialized to and deserialized from JSON and retains the values of all members.

API Usage

var sut = new ClassWithProperties();
sut.Should().BeJsonSerializable();

Alternative Designs

No response

Risks

No response

Are you willing to help with a proof-of-concept (as PR in that or a separate repo) first and as pull-request later on?

Yes, please assign this issue to me.

[dennisdoomen]

I like that. What about you @jnyrup ?