feat(www): enable providers to send custom error responses via the dynamic key

Makefile

@@ -7,7 +7,7 @@ GOBIND=env PATH="$(GOBIN):$(PATH)" "$(GOMOBILE)" bind
 IMPORT_HOST=github.com
 IMPORT_PATH=$(IMPORT_HOST)/Jigsaw-Code/outline-client
 
-.PHONY: android apple linux windows
+.PHONY: android apple linux windows browser
 
 all: android apple linux windows
 
@@ -73,3 +73,6 @@ $(XGO): go.mod
 go.mod: tools.go
 	go mod tidy
 	touch go.mod
+
+browser:
+	echo 'browser environment: nothing to do'

src/www/app/outline_server_repository/access_key_serialization.ts

@@ -36,8 +36,14 @@ export function staticKeyToShadowsocksSessionConfig(staticKey: string): Shadowso
   }
 }
 
-function parseShadowsocksSessionConfigJson(maybeJsonText: string): ShadowsocksSessionConfig | null {
-  const {method, password, server, server_port, prefix} = JSON.parse(maybeJsonText);
+function parseShadowsocksSessionConfigJson(responseBody: string): ShadowsocksSessionConfig | null {
+  const responseJson = JSON.parse(responseBody);
+
+  if ('error' in responseJson) {
+    throw new errors.SessionConfigFetchFailed(responseJson.error.message);
+  }
+
+  const {method, password, server, server_port, prefix} = responseJson;
 
   // These are the mandatory keys.
   const missingKeys = [];