Get current callsign as observer callsign.

This will be used with OBS mode login.

src/blackmisc/avcallsign.cpp

@@ -41,6 +41,18 @@ namespace BlackMisc
             return unified;
         }
 
+        /*
+         * Callsign as Observer
+         */
+        QString CCallsign::getAsObserverCallsignString() const
+        {
+            if (this->isEmpty()) return "";
+            QString obs = this->getStringAsSet();
+            if (obs.endsWith("_OBS", Qt::CaseInsensitive)) return obs;
+            if (obs.contains('_')) obs = obs.left(obs.lastIndexOf('_'));
+            return obs.append("_OBS").toUpper();
+        }
+
         /*
          * Equals callsign?
          */

src/blackmisc/avcallsign.h

@@ -76,11 +76,17 @@ namespace BlackMisc
             const QString &getCallsignPronounced() const { return this->m_callsignPronounced; }
 
             /*!
-             * \brief Get ICAO code, if this possible
+             * \brief Get ICAO code, if this makes sense (EDDF_TWR -> EDDF)
              * \return
              */
             QString getIcaoCode() const { return m_callsign.left(4).toUpper(); }
 
+            /*!
+             * \brief Makes this callsign looking like an observer callsign (DAMBZ -> DAMBZ_OBS)
+             * \return
+             */
+            QString getAsObserverCallsignString() const;
+
             /*!
              * \brief Equals callsign string?
              * \param callsignString