implement minimal (simple) regiment creation

src/openvic-simulation/military/UnitInstanceGroup.cpp

@@ -578,4 +578,40 @@ bool UnitInstanceManager::create_leader(
 	});
 
 	return true;
-}
+}
+
+bool UnitInstanceManager::create_regiment(
+        RegimentType const& regiment_type,
+        Pop& pop,
+        ProvinceInstance& location
+) {
+        CountryInstance* country = location.get_owner();
+        if (OV_unlikely(country == nullptr)) {
+                spdlog::error_s("Trying to recruit regiment in unowned province \"{}\"", location.get_identifier());
+                return false;
+        }
+
+        if (!Pop::is_culture_status_allowed(regiment_type.allowed_cultures, pop.get_culture_status())) {
+                return false;
+        }
+
+        if (!pop.try_recruit()) {
+                return false;
+        }
+
+	//right now the regiment is created at full strength immediately 
+	//XXX TODO: add recruitment times
+        RegimentInstance& regiment = *get_unit_instances<LAND>().insert(
+                [this, &regiment_type, &pop]() -> RegimentInstance {
+                        return { unique_id_counter++, regiment_type.get_identifier(), regiment_type, &pop, false };
+                }()
+        );
+        unit_instance_map.emplace(regiment.unique_id, regiment);
+
+        //always spawns a new army for now
+        ArmyInstance& army = *armies.emplace(unique_id_counter++, regiment_type.get_identifier(), *country, location);
+        unit_instance_group_map.emplace(army.unique_id, army);
+        army.add_unit(regiment);
+
+        return true;
+}

src/openvic-simulation/military/UnitInstanceGroup.hpp

@@ -217,6 +217,7 @@ namespace OpenVic {
 		LeaderInstance* get_leader_instance_by_unique_id(unique_id_t unique_id);
 		UnitInstance* get_unit_instance_by_unique_id(unique_id_t unique_id);
 		UnitInstanceGroup* get_unit_instance_group_by_unique_id(unique_id_t unique_id);
+
 
 		// Creates a new leader of the specified branch and adds it to the specified country. The leader's name and traits
 		// can be specified, but if they are not, the leader will be generated with a random name and traits. The country's
@@ -230,5 +231,12 @@ namespace OpenVic {
 			LeaderTrait const* personality = nullptr,
 			LeaderTrait const* background = nullptr
 		);
+		//this seems too minimal, am i missing something?
+		bool create_regiment(
+			RegimentType const& regiment_type,
+			Pop& pop,
+			ProvinceInstance& location
+		);
+
 	};
 }

src/openvic-simulation/misc/GameAction.cpp

@@ -317,9 +317,5 @@ bool GameActionManager::VariantVisitor::operator() (start_land_unit_recruitment_
 		return false;
 	}
 
-	//these TODO's should be implemented in ProvinceInstance and/or some military type
-	//TODO verify pop's cultural status is acceptable for regiment type
-	//TODO verify pop is recruitable and has enough size (pop.try_recruit())
-	//TODO actually instantiate a regiment in recruitment state
-	return false;
+	return instance_manager.get_unit_instance_manager().create_regiment(*regiment_type, *pop, *province);
 }