Refactor some methods in GasLiftSingleWellGeneric.

Refactor getOilRateWithGroupLimit_(), getGasRateWithGroupLimit_(),
getWaterRateWithGroupLimit_(), and getLiquidRateWithGroupLimit_() into
a single generic method called getRateWithGroupLimit_().

opm/simulators/wells/GasLiftGroupInfo.cpp

@@ -84,6 +84,26 @@ gasTarget(const std::string& group_name)
     return group_rate.gasTarget();
 }
 
+double
+GasLiftGroupInfo::
+getRate(Rate rate_type, const std::string& group_name)
+{
+    switch (rate_type) {
+    case Rate::oil:
+        return oilRate(group_name);
+    case Rate::gas:
+        return gasRate(group_name);
+    case Rate::water:
+        return waterRate(group_name);
+    case Rate::liquid:
+        return oilRate(group_name) + waterRate(group_name);
+    default:
+        // Need this to avoid compiler warning : control reaches end of non-void function
+        throw std::runtime_error("This should not happen");
+    }
+}
+
+
 std::tuple<double, double, double, double>
 GasLiftGroupInfo::
 getRates(int group_idx)
@@ -93,6 +113,25 @@ getRates(int group_idx)
     return std::make_tuple(rates.oilRate(), rates.gasRate(), rates.waterRate(), rates.alq());
 }
 
+std::optional<double>
+GasLiftGroupInfo::
+getTarget(Rate rate_type, const std::string& group_name)
+{
+    switch (rate_type) {
+    case Rate::oil:
+        return oilTarget(group_name);
+    case Rate::gas:
+        return gasTarget(group_name);
+    case Rate::water:
+        return waterTarget(group_name);
+    case Rate::liquid:
+        return liquidTarget(group_name);
+    default:
+        // Need this to avoid compiler warning : control reaches end of non-void function
+        throw std::runtime_error("This should not happen");
+    }
+}
+
 std::vector<std::pair<std::string,double>>&
 GasLiftGroupInfo::
 getWellGroups(const std::string& well_name)
@@ -189,6 +228,23 @@ liquidTarget(const std::string &group_name)
     return group_rate.liquidTarget();
 }
 
+const std::string
+GasLiftGroupInfo::
+rateToString(Rate rate) {
+    switch (rate) {
+    case Rate::oil:
+        return "oil";
+    case Rate::gas:
+        return "gas";
+    case Rate::water:
+        return "water";
+    case Rate::liquid:
+        return "liquid";
+    default:
+        throw std::runtime_error("This should not happen");
+    }
+}
+
 void
 GasLiftGroupInfo::
 update(