Ability to add a language as queryparams for `export`

[KhaledBousrih]

export endpoint should be able to accept the queryparam ?lang= with the value of the language desired for the export (for example fr).

If this queryparam exists, the following should be transalted to the selected language:

• Booleans: for example if ?lang=fr, True becomes VRAI and False becomes FAUX
• datetime and date fields: the value of pendulum with the right locale set should be returned in the format: YYYY/MM/DD HH:mm:ss
• csv headers: the name of the files should be translated depending on a setting in concrete datatsore: this setting is a dict and looks like:

{
  "fr": {
    "filed_name_1": "nom_du_champ_1",
    "filed_name_2": "nom_du_champ_2"
  }
}

[paschembri]

We may have to split the issue into 2 sub-issues :

• standard translations using i18n mechnisms from Django
• dynamic translations for meta data about models definition