Improve exception handling

To make it clearer what went wrong.

src/main/kotlin/MissingSettingException.kt

@@ -18,4 +18,11 @@
 
 package org.memobase
 
-class MissingSettingException(setting: String) : Exception("Missing setting $setting in configuration file. Stopping application ...")
+class MissingSettingException(source: String, setting: String) :
+    Exception(
+        when (source) {
+            "env" -> "Internal Configuration Error: $setting!"
+            "missing" -> "Internal Configuration Error: Missing setting $setting in configuration file."
+            else -> "User Configuration Error: A value for setting $setting is required."
+        }
+    )

src/main/kotlin/SettingsLoader.kt

@@ -45,8 +45,7 @@ class SettingsLoader {
                 load.loadFromInputStream(ClassLoader.getSystemResourceAsStream("app.yml"))
             }
         } catch (ex: MissingEnvironmentVariableException) {
-            log.error(ex.message)
-            exitProcess(1)
+            throw MissingSettingException("env", "${ex.localizedMessage}")
         }
     }
 
@@ -57,14 +56,14 @@ class SettingsLoader {
     val kafkaProducerProperties = Properties()
 
     init {
-        val rawYaml = loadYaml()
         try {
+            val rawYaml = loadYaml()
             val mappedYaml = rawYaml as Map<String, Any>
             val kafkaOptions = mappedYaml["kafka"] as Map<String, Any>
             val topics = kafkaOptions["topic"] as Map<String, String>
             topic = topics["out"].orEmpty()
             if (topic.isEmpty()) {
-                throw MissingSettingException("kafka.topic.out")
+                throw MissingSettingException("missing", "kafka.topic.out")
             }
             rawKafkaProperties = kafkaOptions["producer"] as Map<String, String>
 
@@ -90,7 +89,7 @@ class SettingsLoader {
 
     private fun ensurePropertyIsSet(setting: String, settings: Map<String, String>) {
         if (settings[setting].isNullOrEmpty()) {
-            throw MissingSettingException(setting)
+            throw MissingSettingException("missing", setting)
         }
     }
 
@@ -145,7 +144,7 @@ class SettingsLoader {
             }
             abortIfMissing -> {
                 log.error("Required producer property $propertyName was not set! Aborting...")
-                exitProcess(1)
+                throw MissingSettingException("missing", "kafka.producer.$propertyName")
             }
             else -> log.trace("No value for property $propertyName found")
         }

src/main/kotlin/SftpClient.kt

@@ -41,7 +41,7 @@ class SftpClient(sftpSettings: Map<String, String>) {
             ssh.authPassword(sftpSettings["user"], sftpSettings["password"])
             instance = ssh.newSFTPClient()
         } catch (ex: UserAuthException) {
-            log.error("Invalid user authentication supplied.")
+            log.error("SFTP User Authentication Error: Invalid user authentication supplied.")
             exitProcess(1)
         } catch (ex: Exception) {
             ex.printStackTrace()