message: improve volume streaming method determination
  take content_type of related entry into account
diff: @@ -18,16 +18,20 @@ export function getStreamingMethod(s?: Structure, defaultKind: VolumeServerInfo.
  if (!MmcifFormat.is(model.sourceData)) return defaultKind;
  const { db } = model.sourceData.data;
  + const { db_name, content_type } = db.pdbx_database_related
  - // prefer EMDB entries over structure-factors (SF) e.g. for 'ELECTRON CRYSTALLOGRAPHY' entries
  - // like 6axz or 6kj3 for which EMDB entries are available but map calculation from SF is hard
  + // Prefer EMDB entries over structure-factors (SF) e.g. for 'ELECTRON CRYSTALLOGRAPHY' entries
  + // like 6AXZ or 6KJ3 for which EMDB entries are available but map calculation from SF is hard.
  + // Also check for `content_type` of 'associated EM volume' to exclude cases like 6TEK which
  + // are solved with 'X-RAY DIFFRACTION' but have an related EMDB entry of type 'other EM volume'.
  for (let i = 0, il = db.pdbx_database_related._rowCount; i < il; ++i) {
  - if (db.pdbx_database_related.db_name.value(i).toUpperCase() === 'EMDB') {
  + if (db_name.value(i).toUpperCase() === 'EMDB' && content_type.value(i) === 'associated EM volume') {
  return 'em'
  }
  }
  - if (db.pdbx_database_status.status_code_sf.isDefined && db.pdbx_database_status.status_code_sf.value(0) === 'REL') {
  + const { status_code_sf } = db.pdbx_database_status
  + if (status_code_sf.isDefined && status_code_sf.value(0) === 'REL') {
  return 'x-ray'
  }
  