Read some endpoints on replica db (behind feature flag) (#16677)

Next steps: 
- move some workers' activities to replica db

packages/twenty-server/src/engine/core-modules/feature-flag/enums/feature-flag-key.enum.ts

@@ -15,4 +15,5 @@ export enum FeatureFlagKey {
   IS_DASHBOARD_V2_ENABLED = 'IS_DASHBOARD_V2_ENABLED',
   IS_TIMELINE_ACTIVITY_MIGRATED = 'IS_TIMELINE_ACTIVITY_MIGRATED',
   IS_GLOBAL_WORKSPACE_DATASOURCE_ENABLED = 'IS_GLOBAL_WORKSPACE_DATASOURCE_ENABLED',
+  IS_READ_ON_REPLICA_ENABLED = 'IS_READ_ON_REPLICA_ENABLED',
 }

packages/twenty-server/src/engine/core-modules/twenty-config/config-variables.ts

@@ -834,6 +834,22 @@ export class ConfigVariables {
   })
   PG_DATABASE_URL: string;
 
+  @ConfigVariablesMetadata({
+    group: ConfigVariablesGroup.SERVER_CONFIG,
+    isSensitive: true,
+    description: 'Database connection URL',
+    type: ConfigVariableType.STRING,
+    isEnvOnly: true,
+  })
+  @IsOptional()
+  @IsUrl({
+    protocols: ['postgres', 'postgresql'],
+    require_tld: false,
+    allow_underscores: true,
+    require_host: false,
+  })
+  PG_DATABASE_REPLICA_URL: string;
+
   @ConfigVariablesMetadata({
     group: ConfigVariablesGroup.SERVER_CONFIG,
     description:
@@ -1449,6 +1465,26 @@ export class ConfigVariables {
   })
   @IsOptional()
   AWS_SES_ACCOUNT_ID: string;
+
+  @ConfigVariablesMetadata({
+    group: ConfigVariablesGroup.SERVER_CONFIG,
+    description: 'Timeout in milliseconds for primary database queries',
+    type: ConfigVariableType.NUMBER,
+    isEnvOnly: true,
+  })
+  @CastToPositiveNumber()
+  @IsOptional()
+  PG_DATABASE_PRIMARY_TIMEOUT_MS: number = 10000;
+
+  @ConfigVariablesMetadata({
+    group: ConfigVariablesGroup.SERVER_CONFIG,
+    description: 'Timeout in milliseconds for replica database queries',
+    type: ConfigVariableType.NUMBER,
+    isEnvOnly: true,
+  })
+  @CastToPositiveNumber()
+  @IsOptional()
+  PG_DATABASE_REPLICA_TIMEOUT_MS: number = 10000;
 }
 
 export const validate = (config: Record<string, unknown>): ConfigVariables => {