title: Custom serializer for data class without @Serializable
body: <p>I'm trying to deserialize a JSON file to a Kotlin data class I cannot control using <code>kotlinx.serialization</code>.</p>
  <p>The class looks something along the lines of:</p>
  <pre><code>public data class Lesson(
      val uid: String,
      val start: Instant,
      val end: Instant,
      val module: String,
      val lecturers: List&lt;String&gt;,
      val room: String?,
      val type: String?,
      val note: String?
  )
  </code></pre>
  <p>The JSON I try to parse looks like this:</p>
  <pre><code>{
    &quot;lessons&quot;: [
      {
        &quot;uid&quot;: &quot;sked.de956040&quot;,
        &quot;start&quot;: &quot;2020-11-02T13:30:00Z&quot;,
        &quot;end&quot;: &quot;2020-11-02T16:45:00Z&quot;,
        &quot;module&quot;: &quot;IT2101-Labor SWE I: Gruppe 1 + 2&quot;,
        &quot;lecturers&quot;: [
          &quot;Kretzmer&quot;
        ],
        &quot;room&quot;: &quot;-&quot;,
        &quot;type&quot;: &quot;La&quot;,
        &quot;note&quot;: &quot;Prüfung Online&quot;
      }
    ]
  }
  </code></pre>
  <p>This is tried via:</p>
  <pre><code>@Serializable
  data class ExpectedLessons(
      val lessons: List&lt;Lesson&gt;
  )
  
  val decoded = Json.decodeFromString&lt;ExpectedLessons&gt;(text)
  </code></pre>