feat: Add strict object additionalProperties: false mapping

[samchungy]

According to the Open API Specification:

additionalProperties - Value can be boolean or object. Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema. Consistent with JSON Schema, additionalProperties defaults to true.

According to the Zod Readme:

.passthrough
By default Zod object schemas strip out unrecognized keys during parsing.

This means that we should see alot more of this in the schema if this bit of the code was working:

Since this defaults to true we don't need this passthrough code. Instead I'll add the option to map strict objects.