Add support for specifying the format string for the openspace.time.SPICE() function

include/openspace/util/spicemanager.h

@@ -613,6 +613,9 @@ public:
 
     std::string dateFromEphemerisTime(double ephemerisTime, const char* format);
 
+    void dateFromEphemerisTime(double ephemerisTime, char* outBuf, int bufferSize,
+        const std::string& format = "YYYY MON DDTHR:MN:SC.### ::RND") const;
+
     /**
      * Returns the \p position of a \p target body relative to an \p observer in a
      * specific \p referenceFrame, optionally corrected for \p lightTime (planetary

include/openspace/util/time.h

@@ -136,6 +136,13 @@ public:
      */
     std::string_view UTC() const;
 
+    /**
+     * Returns the current time as a formatted date string. The date string can be
+     * formatted using the SPICE picture parameters as described in
+     * https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/timout_c.html
+     */
+    std::string_view string(const std::string& format) const;
+
     /**
      * Returns the current time as a ISO 8601 formatted, i.e YYYY-MM-DDThh:mm:ssZ.
      *