refactor of model targets and constraints, addition of new constraint types and constraint construction process

app/models/targets/tif_target.py

@@ -0,0 +1,31 @@
+from __future__ import annotations
+from typing import TYPE_CHECKING
+
+from models.targets.target import *
+
+if TYPE_CHECKING:
+    from models.problem import Problem
+
+class TifTarget(Target):
+    def constraints(self, problem_handler: Problem, solver_run: SolverRun):
+        problem_handler.problem += lpSum([
+            bundle.tif(solver_run.irt_model, self.theta)
+            * problem_handler.solver_bundles_var[bundle.id]
+            for bundle in problem_handler.bundles
+        ] + [
+            item.iif(solver_run.irt_model, self.theta) *
+            problem_handler.solver_items_var[item.id]
+            for item in problem_handler.items
+        ]) >= self.minimum(
+        ), f'Min TIF theta({self.theta}) at target {self.value} with a drift % of {self.drift}'
+
+        problem_handler.problem += lpSum([
+            bundle.tif(solver_run.irt_model, self.theta)
+            * problem_handler.solver_bundles_var[bundle.id]
+            for bundle in problem_handler.bundles
+        ] + [
+            item.iif(solver_run.irt_model, self.theta) *
+            problem_handler.solver_items_var[item.id]
+            for item in problem_handler.items
+        ]) <= self.maximum(
+        ), f'Max TIF theta({self.theta}) at target {self.value} with a drift % of {self.drift}'