Update Metadata Endpoint

• Add support for siteClass "NEHRP site classification" input.

  • This input is a string that must be mapped to a vs30.
    • ['A','AB','B','BC','C','CD','D','DE','E'] => [2000, 1500, 1080, 760, 530, 365, 260, 185, 150]
  • The vs30 is then used in the DB query to select the proper region. Only siteClass=BC (vs30=760) is supported by existing reference documents. This (siteClass=BC) should be a default if not provided.
  • Update documentation page for this new parameter.

• Add vs30 and periods to output.

  • Update documentation page for this new output.