Add caching of user-data (#568)

* Add caching of user-data for 600 seconds

* Make cache-entry interface commonly usable

* Extract revision types

* Remove revision-cache rule

* Use seconds as cache-time interval (Date.now uses milliseconds)

* Fix import error

* Extract cache logic into common cache-class

* Add cache class that was forgotten to commit in last commit

* Start adding unit tests

* Fix bug detected during unit-testing

* Add unit tests for cache

* Made entry-limit test more explicit

* Renamed files to lower-case starting letter

src/api/users/index.ts

@@ -1,10 +1,18 @@
+import { Cache } from '../../components/common/cache/cache'
 import { defaultFetchConfig, expectResponseCode, getApiUrl } from '../utils'
 import { UserResponse } from './types'
 
+const cache = new Cache<string, UserResponse>(600)
+
 export const getUserById = async (userid: string): Promise<UserResponse> => {
+  if (cache.has(userid)) {
+    return cache.get(userid)
+  }
   const response = await fetch(`${getApiUrl()}/users/${userid}`, {
     ...defaultFetchConfig
   })
   expectResponseCode(response)
-  return (await response.json()) as UserResponse
+  const userData = (await response.json()) as UserResponse
+  cache.put(userid, userData)
+  return userData
 }