Document Meta Data / Versioning

[mfriesen]

There is a need to allow custom document meta data in addition to Tags. Document meta data would be different to document tags in the following ways:

• Meta Data is versioned (and stored in a different DynamoDB Table)
• Meta Data attributes can have a "type" -> TBD on what kind of types there would be but things like TIMESTAMP, TEXT (max 1000 characters), Date, etc
• would need an endpoint like POST /documents/{documentId}/versionRestore/{versionId} to restore to a previous version
• In addition would need an endpoint to DELETE version like /documents/{documentId}/versions/{versionId}

Rules around deleting a versions would be controlled by #68