Function build_sql_templates_metadata 

pub fn build_sql_templates_metadata(operator_names: &[&str]) -> Value

Build SQL templates metadata for rich filter types.

Generates a JSON structure like:

{
  "operators": {
    "emailDomainEq": {
      "postgres": "SPLIT_PART($field, '@', 2) = $1",
      "mysql": "SUBSTRING_INDEX($field, '@', -1) = ?",
      "sqlite": "...",
      "sqlserver": "..."
    }
  }
}