feat: Enhance currency handling and validation across scenarios

- Updated form template to prefill currency input with default value and added help text for clarity.
- Modified integration tests to assert more descriptive error messages for invalid currency codes.
- Introduced new tests for currency normalization and validation in various scenarios, including imports and exports.
- Added comprehensive tests for pricing calculations, ensuring defaults are respected and overrides function correctly.
- Implemented unit tests for pricing settings repository, ensuring CRUD operations and default settings are handled properly.
- Enhanced scenario pricing evaluation tests to validate currency handling and metadata defaults.
- Added simulation tests to ensure Monte Carlo runs are accurate and handle various distribution scenarios.

schemas/scenario.py

@@ -5,6 +5,7 @@ from datetime import date, datetime
 from pydantic import BaseModel, ConfigDict, field_validator, model_validator
 
 from models import ResourceType, ScenarioStatus
+from services.currency import CurrencyValidationError, normalise_currency
 
 
 class ScenarioBase(BaseModel):
@@ -23,11 +24,15 @@ class ScenarioBase(BaseModel):
     @classmethod
     def normalise_currency(cls, value: str | None) -> str | None:
         if value is None:
-            return value
-        value = value.upper()
-        if len(value) != 3:
-            raise ValueError("Currency code must be a 3-letter ISO value")
-        return value
+            return None
+        candidate = value if isinstance(value, str) else str(value)
+        candidate = candidate.strip()
+        if not candidate:
+            return None
+        try:
+            return normalise_currency(candidate)
+        except CurrencyValidationError as exc:
+            raise ValueError(str(exc)) from exc
 
 
 class ScenarioCreate(ScenarioBase):
@@ -50,11 +55,15 @@ class ScenarioUpdate(BaseModel):
     @classmethod
     def normalise_currency(cls, value: str | None) -> str | None:
         if value is None:
-            return value
-        value = value.upper()
-        if len(value) != 3:
-            raise ValueError("Currency code must be a 3-letter ISO value")
-        return value
+            return None
+        candidate = value if isinstance(value, str) else str(value)
+        candidate = candidate.strip()
+        if not candidate:
+            return None
+        try:
+            return normalise_currency(candidate)
+        except CurrencyValidationError as exc:
+            raise ValueError(str(exc)) from exc
 
 
 class ScenarioRead(ScenarioBase):
@@ -75,7 +84,8 @@ class ScenarioComparisonRequest(BaseModel):
     def ensure_minimum_ids(self) -> "ScenarioComparisonRequest":
         unique_ids: list[int] = list(dict.fromkeys(self.scenario_ids))
         if len(unique_ids) < 2:
-            raise ValueError("At least two unique scenario identifiers are required for comparison.")
+            raise ValueError(
+                "At least two unique scenario identifiers are required for comparison.")
         self.scenario_ids = unique_ids
         return self