docs(docstrings): add docstrings to public method interfaces (#25)

- Resolves #18

Reviewed-on: #25

src/main/java/com/ddf/vodsystem/dto/CommandOutput.java

@@ -10,6 +10,11 @@ public class CommandOutput {
     private List<String> output = new ArrayList<>();
     private int exitCode;
 
+    /**
+     * Appends a line to the captured command output.
+     *
+     * @param line the output line to append
+     */
     public void addLine(String line) {
         output.add(line);
     }