Adds file type detection, and beefs up error states for file uploads

src/main/kotlin/net/halfbinary/scavengerhuntapi/service/FileProbeService.kt

@@ -0,0 +1,22 @@
+package net.halfbinary.scavengerhuntapi.service
+
+import org.apache.tika.Tika
+import org.apache.tika.config.TikaConfig
+import org.springframework.stereotype.Service
+
+
+@Service
+class FileProbeService {
+    private val tika = Tika()
+
+    fun getFileType(fileBytes: ByteArray): String {
+        return tika.detect(fileBytes)
+    }
+
+    fun getFileExtension(fileType: String): String {
+        return TikaConfig.getDefaultConfig().mimeRepository.forName(fileType).extension
+    }
+    fun isImageType(fileType: String): Boolean {
+        return fileType.startsWith("image")
+    }
+}