Fix 159 rig json

[jtyoung84]

Closes #159

• Short-term patch to loosen restriction of pydantic validation and serialization. If a model json file is json serializable, we'll build the metadata record and flag the record as being invalid instead of raising an error and terminating the GatherMetadataJob
• Adds problematic rig.json in test folder
• Long-term, this logic should move to the aind-data-schema repo