Rename APPSIGNAL_ENVIRONMENT to public env version

Rename the internal APPSIGNAL_ENVIRONMENT env var to the publicly known
APPSIGNAL_APP_ENV env var.

This makes all the agent config options consistent with each other.

[skip changeset] because it requires an agent update that will include
a changeset.

src/__tests__/config.test.ts

@@ -223,13 +223,13 @@ describe("Configuration", () => {
 
     it("writes default configuration values to the environment", () => {
       expect(env("_APPSIGNAL_ACTIVE")).toBeUndefined()
+      expect(env("_APPSIGNAL_APP_ENV")).toBeDefined()
       expect(env("_APPSIGNAL_APP_NAME")).toBeUndefined()
       expect(env("_APPSIGNAL_CA_FILE_PATH")).toMatch(/cert\/cacert\.pem$/)
       expect(env("_APPSIGNAL_DNS_SERVERS")).toBeUndefined()
       expect(env("_APPSIGNAL_ENABLE_HOST_METRICS")).toEqual("true")
       expect(env("_APPSIGNAL_ENABLE_STATSD")).toBeUndefined()
       expect(env("_APPSIGNAL_ENABLE_NGINX_METRICS")).toBeUndefined()
-      expect(env("_APPSIGNAL_ENVIRONMENT")).toBeDefined()
       expect(env("_APPSIGNAL_FILES_WORLD_ACCESSIBLE")).toEqual("true")
       expect(env("_APPSIGNAL_FILTER_DATA_KEYS")).toBeUndefined()
       expect(env("_APPSIGNAL_HOSTNAME")).toBeUndefined()

src/config/configmap.ts

@@ -36,13 +36,13 @@ export const ENV_TO_KEY_MAPPING: Record<string, keyof AppsignalOptions> = {
 
 export const PRIVATE_ENV_MAPPING: Record<string, keyof AppsignalOptions> = {
   _APPSIGNAL_ACTIVE: "active",
+  _APPSIGNAL_APP_ENV: "environment",
   _APPSIGNAL_APP_NAME: "name",
   _APPSIGNAL_CA_FILE_PATH: "caFilePath",
   _APPSIGNAL_DNS_SERVERS: "dnsServers",
   _APPSIGNAL_ENABLE_HOST_METRICS: "enableHostMetrics",
   _APPSIGNAL_ENABLE_STATSD: "enableStatsd",
   _APPSIGNAL_ENABLE_NGINX_METRICS: "enableNginxMetrics",
-  _APPSIGNAL_ENVIRONMENT: "environment",
   _APPSIGNAL_FILES_WORLD_ACCESSIBLE: "filesWorldAccessible",
   _APPSIGNAL_FILTER_PARAMETERS: "filterParameters",
   _APPSIGNAL_FILTER_SESSION_DATA: "filterSessionData",