Fixed @tommi27 uniqueness frenzy for rooms

I have now discovered the Schadenfreude in using git-blame. To quote an
old commit message from high school:

[Trascrizione domande fisica e correzione di GRAVISSIMI bug presenti nel
codici di Maggioni](dd0933def0)

```
La trascrizione dei test è stata fatta in modo certosino, simile a
quello dei monaci emanuensi.
I GRAVISSIMI buggg (3 g perchè fa faigo) potevano rendere il sito
incomprensibile
```

.gitlab-ci.yml

@@ -11,6 +11,8 @@ stages:
 smarthut_deploy:
   stage: deploy
   image: docker:latest
+  tags:
+    - dind
   services:
     - docker:dind
   variables:

src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Device.java

@@ -49,17 +49,13 @@ public abstract class Device {
      * The name for the category of this particular device (e.g 'dimmer'). Not stored in the
      * database but set thanks to constructors
      */
-    @ApiModelProperty(hidden = true)
-    @Transient
-    private final String kind;
+    @Transient private final String kind;
 
     /**
      * The way this device behaves in the automation flow. Not stored in the database but set thanks
      * to constructors
      */
-    @ApiModelProperty(hidden = true)
-    @Transient
-    private final FlowType flowType;
+    @Transient private final FlowType flowType;
 
     public long getId() {
         return id;

src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Room.java

@@ -139,7 +139,7 @@ public class Room {
      * inserting from a REST call.
      */
     @NotNull
-    @Column(name = "user_id", nullable = false, unique = true)
+    @Column(name = "user_id", nullable = false)
     private Long userId;
 
     /** The user given name of this room (e.g. 'Master bedroom') */