Start maintaining tables that are not fully standardized

Background

There are multiple tables which are explicitly required/referenced by different tools, and are currently de facto part of OMOP standard, but that do not have sufficient maintained documentation, so their status as a part of canonical OMOP CDM tables is unclear. We need to take ownership of those tables and host proper documentation for them, or explicitly discard them as implementation details only specific to tools using them -- so documentation has to be hosted on that side.

Old wiki references some of those tables, but is also marked as outdated.

We need to add following to the wiki:

1. Categorized list of extra tables
2. DDL where possible
3. Reference implementations (e.g. for *_ERA derived tables)

Categories

Deprecated tables

Tables that are in active use and enjoy tool support, but have outdated design or superseded by other tables or solutions. Case in point – SOURCE_TO_CONCEPT_MAP, which is no longer sufficient to host full spectrum of possible source to concept relationships, but is still part of OMOP CDM with tool (Usagi) support, and is used in ETL.

This tables must have documented deprecation strategy for implementers, preferrably with reference implementations.

Examples:

• #725
• #727

Derived patient data tables

*_ERA tables enjoy first-class support in Atlas, but they are not sufficiently documented anywhere. HADES packages provide a reference implementation, but there is no high-level design overview for them on the wiki, which just contains stub articles. We need to document a high-level strategy for how era derivation works, and link to the external documentation and HADES manuals and code.

Examples:

• CONDITION_ERA
• DRUG_ERA
• DOSE_ERA

Vocabulary metadata tables

Note that #726 is not here, because dosage information is incomplete without PACK_CONTENT.

Examples:

• #728
• CONCEPT_METADATA and CONCEPT_RELATIONSHIP_METADATA

Start with the outdated standardized-derived-elements wiki page and review the linked issues #725, #726, #727, and #728. Compare the existing stubs with HADES manuals and code, Atlas support, and the Vocabulary Metadata page. Done means the wiki has categorized tables, available DDL, deprecation guidance, and reference implementations or links for derived tables.