Added database persistence ability

app/src/main/java/com/denizk0461/studip/db/EventDatabase.kt

@@ -0,0 +1,30 @@
+package com.denizk0461.studip.db
+
+import android.content.Context
+import androidx.room.Database
+import androidx.room.Room
+import androidx.room.RoomDatabase
+import com.denizk0461.studip.data.StudIPEvent
+
+@Database(entities = [StudIPEvent::class], version = 1)
+abstract class EventDatabase : RoomDatabase() {
+
+    abstract fun dao(): EventDAO
+
+    companion object {
+        private var instance: EventDatabase? = null
+
+        fun getInstance(context: Context): EventDatabase {
+            if (instance == null) {
+                synchronized(EventDatabase::class) {
+                    instance = Room.databaseBuilder(
+                        context.applicationContext,
+                        EventDatabase::class.java,
+                        "event_db"
+                    ).build()
+                }
+            }
+            return instance!!
+        }
+    }
+}