Add support for Paraguay TIN

[unho]

RUC online search:

• Query form: https://www.documentos.gov.py/simple/etapas/ejecutar/1369034
• Another web to query RUC: https://www.ruc.com.py/
• Yet another RUC query page: https://rucparaguay.com/

Get RUC examples:

• To get a list of RUC open pages from this Google search: https://www.google.com/search?q=site%3Acontrataciones.gov.py+inurl%3A%2Fproveedor%2F
• Search company names in https://www.icex.es/icex/wcm/idc/groups/public/documents/documento/mde2/njgy/~edisp/doc2016682980.pdf in https://www.ruc.com.py/
• Search for common words in company names in https://www.ruc.com.py/ (or in https://rucparaguay.com/) like "AGENCIA" or "Compañia", "consorcio", "empresa", "international"...
• List of RUCs (the ZIP files) containing a CSV file whose columns are "RUC (with no verification digit)", "name", "verification digit", "old RUC". This includes both physical and juridical persons RUCs: https://www.set.gov.py/portal/PARAGUAY-SET/InformesPeriodicos?folder-id=repository:collaboration:/sites/PARAGUAY-SET/categories/SET/Informes%20Periodicos/listado-de-ruc-con-sus-equivalencias

Implementations:

• Python implementation (seems to validate both physical and juridical persons RUC numbers): https://github.com/BlasFerna/py-ruc-calc
• Algorithm in various programming languages: https://www.set.gov.py/portal/PARAGUAY-SET/detail?content-id=/repository/collaboration/sites/PARAGUAY-SET/documents/herramientas/digito-verificador.pdf
• Another implementation: https://gitlab.com/snippets/1667476
• And another one: https://www.lawebdelprogramador.com/codigo/FoxPro-Visual-FoxPro/2327-Calcular-Digito-Verificador-del-RUC-Paraguay.html

More info:

• Article with more info (possibly outdated): http://www.abc.com.py/edicion-impresa/economia/tributacion-responde-a-las-preguntas-mas-frecuentes-de-los-contribuyentes-963633.html