DocumentDb Mapping (for initial release)

[dlvenable]

This is a high-level task for tracking changes to the documentdb source to improve the type mappings.

• DocumentDb simple representations of BSON types #4458
• Support DocumentDb types: Null, Undefined, MinKey, MaxKey #4459
• Export BSON Decimal as BigDecimal from DocumentDb source #4462
• Create a doc_id field for data exported from the DocumentDb source #4463
• Support conditional expression to evaluate based on the data type for a given field #4478
• Support encoding JSON #832
• Include BSON type information in the Event metadata to allow for conversions #4491
• Investigation into whether Data Prepper retains map order (using LinkedHashMap over HashMap).

See #4490 for mappings that will not be available at the first release of 2.8.