make default atproto proxy an env var

cmd/cocoon/main.go

···
 				Name:    "session-secret",
 				EnvVars: []string{"COCOON_SESSION_SECRET"},
 			},
+			&cli.StringFlag{
+				Name:    "default-atproto-proxy",
+				EnvVars: []string{"COCOON_DEFAULT_ATPROTO_PROXY"},
+				Value:   "did:web:api.bsky.app#bsky_appview",
+			},
 		},
 		Commands: []*cli.Command{
 			runServe,
···
 				AccessKey:      cmd.String("s3-access-key"),
 				SecretKey:      cmd.String("s3-secret-key"),
 			},
-			SessionSecret: cmd.String("session-secret"),
+			SessionSecret:       cmd.String("session-secret"),
+			DefaultAtprotoProxy: cmd.String("default-atproto-proxy"),
 		})
 		if err != nil {
 			fmt.Printf("error creating cocoon: %v", err)

server/handle_proxy.go

···
 
 	svc := e.Request().Header.Get("atproto-proxy")
 	if svc == "" {
-		svc = "did:web:api.bsky.app#bsky_appview" // TODO: should be a config var probably
+		svc = s.config.DefaultAtprotoProxy
 	}
 
 	svcPts := strings.Split(svc, "#")

server/server.go

···
 	S3Config *S3Config
 
 	SessionSecret string
+
+	DefaultAtprotoProxy string
 }
 
 type config struct {
-	Version        string
-	Did            string
-	Hostname       string
-	ContactEmail   string
-	EnforcePeering bool
-	Relays         []string
-	AdminPassword  string
-	SmtpEmail      string
-	SmtpName       string
+	Version             string
+	Did                 string
+	Hostname            string
+	ContactEmail        string
+	EnforcePeering      bool
+	Relays              []string
+	AdminPassword       string
+	SmtpEmail           string
+	SmtpName            string
+	DefaultAtprotoProxy string
 }
 
 type CustomValidator struct {
···
 		plcClient:  plcClient,
 		privateKey: &pkey,
 		config: &config{
-			Version:        args.Version,
-			Did:            args.Did,
-			Hostname:       args.Hostname,
-			ContactEmail:   args.ContactEmail,
-			EnforcePeering: false,
-			Relays:         args.Relays,
-			AdminPassword:  args.AdminPassword,
-			SmtpName:       args.SmtpName,
-			SmtpEmail:      args.SmtpEmail,
+			Version:             args.Version,
+			Did:                 args.Did,
+			Hostname:            args.Hostname,
+			ContactEmail:        args.ContactEmail,
+			EnforcePeering:      false,
+			Relays:              args.Relays,
+			AdminPassword:       args.AdminPassword,
+			SmtpName:            args.SmtpName,
+			SmtpEmail:           args.SmtpEmail,
+			DefaultAtprotoProxy: args.DefaultAtprotoProxy,
 		},
 		evtman:   events.NewEventManager(events.NewMemPersister()),
 		passport: identity.NewPassport(h, identity.NewMemCache(10_000)),