fix: 1702: Fix getExceptionMessageInfo() and add docu

Fix getExceptionMessageInfo() function in exception-helper and add some
documentation to logger.exception

Closes: hyperledger#1702
Signed-off-by: Michael Courtin <michael.courtin@accenture.com>

packages/cactus-common/src/main/typescript/exception/exception-helper.ts

@@ -38,7 +38,7 @@ export class ExceptionHelper {
     const exceptionMessageInfo = this.getExceptionMessageInfo(exception);
     const exceptionStackInfo = this.getExceptionStackInfo(exception);
     let content = "";
-    let runtimeError = new RuntimeError(context, exceptionMessageInfo.message);
+    let runtimeError: RuntimeError | undefined = undefined;
 
     if (exception instanceof Error) {
       // scenario 1:  exception is already an instance of Error / RuntimeError -> can be used directly
@@ -212,6 +212,9 @@ export class ExceptionHelper {
       if (!exceptionHandled && isOfTypeString) {
         message = customExceptionPrefix + exception;
         exceptionHandled = true;
+        // as this scenario handles exception of string only type
+        // there is no other property and it is per se completely stringified
+        containsCompleteStringifiedException = true;
       }
 
       // scenario 4:  handling of custom exceptions

packages/cactus-common/src/main/typescript/logging/logger.ts

@@ -119,6 +119,14 @@ export class Logger {
   }
 
   /**
+   * The 'exception' method is retrieving and stringify-ing the complete exception content like message + stack + custom properties (if available) in a safe and secure way
+   * of any arbitrary exception or whatever it might be and logging it as an error thru the usage of this logger.error() functionality.
+   *
+   * So there is no need of dealing with different exception types or checks if a stack trace etc. is available -> all is done automatically here
+   * Only hand in the exception and maybe some optional, additional information / context can be provided as second parameter about the scenario where the exception happened
+   *
+   *
+   *
    * Standard Exception Handling:
    * ============================
    * logger.exception(ex);