docs(backend): create new folder in doc to contain linking universities process

documentation/ProdRelated/maintenance/linking_universities.md

+# Linking Universities
+
+## Problem description
+
+Data from UTC DSI is automatically updated every day.
+However, we need to link new university data from the DSI with universities on REX-DRI to guarantee data integrity (there might be duplicates on the DSI side) and correctness. Unlinked universities ids and names are displayed on this route: [https://rex.dri.utc.fr/app/about/unlinked-universities](https://rex.dri.utc.fr/app/about/unlinked-universities).
+
+## Linking (DSI) partners and (REX-DRI) universities
+
+There are two cases:
+
+1. The university (on REX-DRI) already exists. Go to [https://rex.dri.utc.fr/admin](https://rex.dri.utc.fr/admin), select the Partner object with the correct id. Then link it to the right university object.
+
+2. The university does not exist. Go to [https://rex.dri.utc.fr/admin](https://rex.dri.utc.fr/admin) create a new University object, with all its information (website, coordinates, etc.). Then select the Partner object with the corresponding id and link it with the university just created (just like in case 1.).
+
+## Updating denormalized information
+
+After you have done either 1. or 2., you **must** update the denormalized information on the universities. Administrators can do it from the trigger_cron admin page: [https://rex.dri.utc.fr/admin/trigger_cron](https://rex.dri.utc.fr/admin/trigger_cron). Click on update extra denormalization to update information about universities.

documentation/ProdRelated/maintenance/update_major_minor.md

+# Update majors / minors
+
+In case of changes of majors / minors at the UTC, the frontend filter utils need to be updated.
+
+In `frontend/src/utils/majorMinorMappings.js`, each change has to be added as a new line in either `majorMapping` or `minorMapping` like this:
+
+```js
+export const majorMapping = {
+  oldMajorName: "newMajorName"
+};
+
+export const minorMapping = {
+  majorName: {
+    oldMinorName: "newMinorName"
+  }
+};
+```