Add i18n ADR (#1794)

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docs/adr/adr_i18n.md

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+# ADR: Adapt boxtribute for internationalization
+
+[Trello-card](https://trello.com/c/jkdpDyyX/761-check-localization-and-language-options-implementation-in-new-old-app-database?search_id=7c64905c-bda4-4164-9703-9e6a6a933e28)
+
+Decision Deadline: Dec 1st 2024
+
+Author: [Philipp](https://github.com/orgs/boxwise/people/pylipp)
+
+## Status
+
+Proposed.
+
+## Context / Problem Statement
+
+Internationalization (i18n) is the process of designing and developing software so it can be adapted for users of different cultures and languages.
+
+Currently, the boxtribute web app is not capable of providing i18n support. This hinders e.g. the adaption by users in non-English speaking communities.
+
+## Decision Drivers
+
+1. Reliability (are the selected tools popular and maintained?)
+1. Integration (are the selected tools straightforward to integrate into the our existing tools and services?)
+1. Simplicity (are the selected tools easy to use?)
+1. Code readability (is the produced code easy to understand?)
+1. Standardisation (do the selected tools adhere to available standards?)
+1. Financial cost (are the selected tools inexpensive to use?)
+
+It needs to be distinguished between changes of dropapp, v2, and/or external services such as Auth0.
+
+### dropapp
+
+In dropapp translation of text has been adopted in some cases inside a table for translation. The issue with this approach is that for every translation a query is required to get the text.
+
+Translations exist for French and Dutch, along with the default English.
+
+Using a browser-translation tool would remove the need to perform any implementation efforts on this end.
+
+User settings are currently configured via dropapp, hence we'd have to consider an extension such that users can set their preferred language.
+
+### Auth0
+
+We most likely want to store user preference for a language in the user management system.
+
+### v2
+
+Due to the client-server architecture of the v2 web application, translatable text is defined in the front-end. Most of the rest of this document focuses on finding a suitable tool to integrate into the v2 React front-end.
+
+### Translation management system (TMS)
+
+A TMS supports in managing translations in software, and facilitates cooperation between devs, designers, and translators. Popular open-source solutions are e.g.
+- Tolgee (1k texts for free, then €25/mo): https://tolgee.io/apps-integrations/react
+- Weblate (free plan for libre projects): https://weblate.org/en/hosting/
+- Locize (special offer for open-source projects): https://locize.com/open-source.html
+
+## Considered Options
+
+The two most popular i18n tools for React:
+
+### `react-intl`
+
+- 1.6M weekly downloads from npm
+- Uses ICU standard
+- Requires custom solution for translation file loading and locale detection
+- support for complex plurals, date formatting, and number formatting
+- CLI for message extraction and and Translation Management System (TMS) support
+- bundled size of 18kB (gzipped and minified)
+- supports IE11 & 2 most recent versions of Edge, Chrome, Firefox & Safari
+- using react-intl in React Native, make sure your runtime has built-in Intl support
+
+### `react-i18next`
+
+- 3.8M weekly downloads from npm
+- built-in locale switcher
+- ICU standard and message extraction through addons
+- Plugins for async translation file loading and locale detection
+- support for complex plurals, date formatting, and number formatting
+- Fairly large bundled size of 23kB (gzipped and minified)
+- react-i18next is optimally suited for server-side rendering (does not apply to the FE!?)
+
+### Comparison of the APIs
+
+**react-intl**
+
+```javascript
+import {FormattedMessage} from 'react-intl';
+
+<FormattedMessage
+ description="Name introduction" // Description should be a string literal
+ defaultMessage="My name is {name}" // Message should be a string literal
+ values={
+   {
+     name: userName,
+   } // Values should be an object literal, but not necessarily every value inside
+ }
+/>
+```
+
+**react-i18next**
+
+```javascript
+import { useTranslation } from 'react-i18next';
+
+export function MyComponent() {
+  // not passing any namespace will use the defaultNS (by default set to 'translation')
+  const { t, i18n } = useTranslation();
+  return <p>{t('my translated text')}</p>
+}
+```
+
+## Decision
+
+The presented react-packages are on a par with each other in terms of the decision criteria above.
+
+The resulting code style of each solution is probably subject to individual taste however `react-i18next` is decoupled from React in terms of testability and ease of building tools on top of it.
+
+For `react-intl`, an experimental integration into v2 can be found [here](https://github.com/boxwise/boxtribute/pull/1753).
+
+For `react-i18next`, an experimental integration into v2 can be found [here](https://github.com/boxwise/boxtribute/compare/experiment-with-react-i18next).
+
+Using a TMS might not be worth the additional cost and maintenance effort, given that boxtribute (v2) is a fairly small application.
+
+## Consequences / effort estimation
+
+### Initial steps
+
+**Infrastructure** (20h)
+- Install i18n package
+- Set up workflow such that newly added text is auto-extracted (warn about missing translation)
+- Ensure that translation files are shipped with the deployed FE bundle
+- OPTIONAL (extra 20h): integrate TMS (cloud-repo and/or cloud-CI integration)
+
+**Prepare codebase** (50h)
+- Find all text components in FE code, and wrap them such that they can be extracted and replaced
+
+**Translation** (20-50h per language; depends on abilities of translator, and potential copying effort)
+- Extract messages and actually translate them (into the desired languages)
+
+### Development cycle
+
+- Devs have to remember to wrap new text components to make them translatable
+- Translations are best provided during the design phase already
+- Translations are entered into the translation storage
+- Effective translation updates require a production deploy
+- The app should be reviewed in different languages to catch e.g. alignment or overflow glitches
+
+## Open questions
+
+- [Caveat for react-intl compatibility with React-native](https://formatjs.github.io/docs/guides/runtime-requirements#react-native)
+- consider localization for displayed numbers (amount, price, date, time, ...)?
+
+## References
+
+https://phrase.com/blog/posts/react-i18n-best-libraries/
+
+https://formatjs.github.io/docs/getting-started/installation#minimal-application
+https://github.com/PhraseApp-Blog/react-i18n-libraries-2022/tree/react-intl
+https://phrase.com/blog/posts/localizing-react-apps-with-i18next
+
+https://react.i18next.com/guides/quick-start
+https://react.i18next.com/guides/the-drawbacks-of-other-i18n-solutions#the-drawbacks
+https://react.i18next.com/misc/using-with-icu-format#extend-the-i18n-instance-with-icu-module
+https://github.com/i18next/react-i18next/tree/master/example/react
+https://www.i18next.com/