Add a new language

When a recipe has to be configured, the list of language displayed in the UI is limited to languages already used in another recipe of the same Zimfarm instance.

In order to create a new recipe with a new language that is not yet used, the following process must be followed:

• editor creates the new recipe (by cloning an existing one for now) and configures everything but the language (since it is not possible) ; the recipe must be disabled at the stage, and must not be requested
• editor requests help from a developer (by opening a ticket in this openzim/zimfarm repo) to ask for language modification. Information needed is:
  • Zimfarm instance (probably farm.openzim.org, but it is always better to confirm)
  • Recipe name (to fix with proper language)
  • Language code (2 letters, from ISO-639-1, see https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes)
  • Language name (displayed in the UI, in English)
• developer alter the recipe language directly in the database and closes the issue
• editor check that configuration is ok and enable the recipe