Make all api fields snake_case (#105)

Change all snake/camelCase mix and match to camelCase everywhere

Fix conversion to not interfer with service interceptors

Add dynamic conversion between camelCase and snake_case to services

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/frontend/pulls/105

package.json

@@ -9,10 +9,12 @@
   },
   "dependencies": {
     "bulma": "0.8.2",
+    "camel-case": "^4.1.1",
     "copy-to-clipboard": "3.3.1",
     "date-fns": "2.12.0",
     "lodash": "4.17.15",
     "register-service-worker": "1.7.1",
+    "snake-case": "^3.0.3",
     "v-tooltip": "2.0.3",
     "verte": "0.0.12",
     "vue": "2.6.11",