Rename test and add credit

src/main/java/eu/m724/wtapi/provider/twilight/SimpleTwilightTimeProvider.java

@@ -8,6 +8,11 @@ import java.time.LocalDate;
 
 import static java.lang.Math.*;
 
+/**
+ * Calculates approximate sunrise and sunset times
+ * Usually off by a few minutes, except the Poles which, during polar days, are up to few hours inaccurate
+ * Adapted from: <a href="https://gml.noaa.gov/grad/solcalc/solareqns.PDF">https://gml.noaa.gov/grad/solcalc/solareqns.PDF</a>
+ */
 public class SimpleTwilightTimeProvider extends TwilightTimeProvider {
     @Override
     public Twilight calculateTwilightTime(LocalDate date, Coordinates coordinates) {

src/test/java/eu/m724/wtapi/twilight/SimpleTwilightTimeTest.java

@@ -8,7 +8,7 @@ import org.junit.Test;
 
 import java.time.LocalDate;
 
-public class ApproximateTwilightTimeTest {
+public class SimpleTwilightTimeTest {
     /**
      * Acceptable discrepancy in minutes
      */