validate env booleans as true/false strings only.

Avoid @IsBoolean with implicit conversion mismatching isEnabled(); add tests and shared BOOLEAN_STRING_VALUES.

backend/src/config/validate.ts

@@ -1,5 +1,7 @@
 import { plainToClass } from 'class-transformer';
-import { IsBoolean, IsEnum, IsNotEmpty, IsNumber, IsString, Max, Min, validateSync } from 'class-validator';
+import { IsEnum, IsIn, IsNotEmpty, IsNumber, IsString, Max, Min, validateSync } from 'class-validator';
+import { BOOLEAN_STRING_VALUES } from '../consts/booleanStringValues';
+import type { BooleanStringValue } from '../types/BooleanStringValue';
 import { NodeEnv } from '../types/NodeEnv';
 
 class EnvironmentVariables {
@@ -36,8 +38,8 @@ class EnvironmentVariables {
     POSTGRES_PORT: number;
 
     @IsNotEmpty()
-    @IsBoolean()
-    POSTGRES_MIGRATIONS_RUN: boolean;
+    @IsIn(BOOLEAN_STRING_VALUES)
+    POSTGRES_MIGRATIONS_RUN: BooleanStringValue;
 
     @IsNotEmpty()
     @IsString()
@@ -56,8 +58,8 @@ class EnvironmentVariables {
     MULTER_MAX_FILE_BYTES: number;
 
     @IsNotEmpty()
-    @IsBoolean()
-    ALTCHA_ENABLED: boolean;
+    @IsIn(BOOLEAN_STRING_VALUES)
+    ALTCHA_ENABLED: BooleanStringValue;
 
     @IsNotEmpty()
     @IsString()