Implement JGI-style validation rules for OrganismSample ribosomal sequences

[turbomam]

Context

PR #2884 adds ribosomal sequence slots from JGI Isolate v19 to OrganismSample. JGI enforces validation rules that are not yet implemented in the schema:

• 16S sequence must be >1300 nt with <10% Ns for microbial drafts
• ITS sequence must be >450 nt with <2% Ns for fungal drafts
• Sequences must contain only A, C, G, T, or N characters with no header

Per @aclum's review comment, we need to sort out how to implement these validation rules in LinkML.

Options

• LinkML pattern constraints on the slot
• Custom validation in the submission portal
• Post-validation via a separate tool

Related

• PR Add OrganismSample class as subclass of Sample #2884
• JGI Isolate (NA) v19 submission form specification

[turbomam]

Partial progress in PR #2884 (commit 4f80cca): added pattern: '^[ACGTNacgtn]+$' to both ribosomal_sequence and second_ribosomal_sequence slots. Still open: length validation (>1300nt for 16S, >450nt for ITS) and the broader question of how to implement JGI's internal validation rules in the schema.