Translation catalogue loading from classpath EDN resources.

SHELL FUNCTION: performs I/O (classpath resource loading).

The catalogue is a nested map:
  {locale-keyword {translation-key string-or-plural-map}}

Example:
  {:en {:user/sign-in "Sign in"
        :user/greeting {:one "Hello {name}" :many "Hello everyone"}}
   :nl {:user/sign-in "Aanmelden"
        :user/greeting {:one "Hallo {name}" :many "Hallo iedereen"}}}

Ring middleware for i18n — injects locale and translation function into requests.

SHELL FUNCTION: wraps Ring handler (performs I/O boundary).

The middleware stores the catalogue and config on the request so that
locale resolution can happen at render time (after authentication
middleware has added :user to the request).

Injects into request:
  :i18n/catalogue     - the loaded translation catalogue
  :i18n/default-locale - configured default locale keyword
  :i18n/locale-chain  - ordered vector of locale keywords, e.g. [:nl :en]
  :i18n/t             - translation function (key params? n?) → string

Integrant wiring for the i18n module.

Config key: :wagoe/i18n

Example (development):
  :wagoe/i18n {:catalogue-paths ["wagoe/i18n/translations"
                                    "my_app/i18n/translations"]
                  :default-locale :en
                  :dev? true}

Example (production):
  :wagoe/i18n {:catalogue-path "wagoe/i18n/translations"
                  :default-locale :en}

Hiccup renderer that resolves [:t ...] markers to strings.

SHELL FUNCTION: calls hiccup2.core/html (I/O boundary for HTML output).

Marker syntax:
  [:t :key]                  → (t-fn :key)
  [:t :key {:param val}]     → (t-fn :key {:param val})
  [:t :key {:n 3} 3]         → (t-fn :key {:n 3} 3)
  [:t :key nil 3]            → (t-fn :key {} 3)

Dev mode wraps each resolved marker in:
  [:span {:data-i18n (str key)} translated-string]