depth should be required for relevant sample types, like soil

[mslarae13]

depth should not be required for all biosamples.

NMDC schema should

• Split out subclasses for different sample types (soil, plant, water)
• slots should be identified as required or recommended based on sample type

Criteria for completion

• Schema classes updated
• schema slots updated
• slot updates are present in submission portal

[mslarae13]

In relation, depth is currently listed an required for host-associated in the submission schema.
Is depth in host-associated required in the schema?
Need to make depth NOT required for host-associated in submission schema.

[mslarae13]

microbiomedata/submission-schema#150 closes this. The separation of requirement level is managed in the submission schema.