Refactor test cases for improved readability and consistency

- Updated test functions in various test files to enhance code clarity by formatting long lines and improving indentation.
- Adjusted assertions to use multi-line formatting for better readability.
- Added new test cases for theme settings API to ensure proper functionality.
- Ensured consistent use of line breaks and spacing across test files for uniformity.

models/scenario.py

@@ -20,19 +20,16 @@ class Scenario(Base):
     updated_at = Column(DateTime(timezone=True), onupdate=func.now())
     parameters = relationship("Parameter", back_populates="scenario")
     simulation_results = relationship(
-        SimulationResult, back_populates="scenario")
-    capex_items = relationship(
-        Capex, back_populates="scenario")
-    opex_items = relationship(
-        Opex, back_populates="scenario")
-    consumption_items = relationship(
-        Consumption, back_populates="scenario")
+        SimulationResult, back_populates="scenario"
+    )
+    capex_items = relationship(Capex, back_populates="scenario")
+    opex_items = relationship(Opex, back_populates="scenario")
+    consumption_items = relationship(Consumption, back_populates="scenario")
     production_output_items = relationship(
-        ProductionOutput, back_populates="scenario")
-    equipment_items = relationship(
-        Equipment, back_populates="scenario")
-    maintenance_items = relationship(
-        Maintenance, back_populates="scenario")
+        ProductionOutput, back_populates="scenario"
+    )
+    equipment_items = relationship(Equipment, back_populates="scenario")
+    maintenance_items = relationship(Maintenance, back_populates="scenario")
 
     # relationships can be defined later
     def __repr__(self):