Fix errcheck issue in oauth.go (#28795)

server/.golangci.yml

@@ -246,7 +246,6 @@ issues:
         channels/store/storetest/user_store.go|\
         channels/testlib/helper.go|\
         channels/utils/license_test.go|\
-        channels/web/oauth.go|\
         channels/web/oauth_test.go|\
         channels/web/saml.go|\
         channels/web/static.go|\

server/channels/web/oauth.go

@@ -78,7 +78,10 @@ func authorizeOAuthApp(c *Context, w http.ResponseWriter, r *http.Request) {
 	auditRec.Success()
 	c.LogAudit("success")
 
-	w.Write([]byte(model.MapToJSON(map[string]string{"redirect": redirectURL})))
+	_, err = w.Write([]byte(model.MapToJSON(map[string]string{"redirect": redirectURL})))
+	if err != nil {
+		c.Logger.Error("Error writing response", mlog.Err(err))
+	}
 }
 
 func deauthorizeOAuthApp(c *Context, w http.ResponseWriter, r *http.Request) {
@@ -201,7 +204,10 @@ func authorizeOAuthPage(c *Context, w http.ResponseWriter, r *http.Request) {
 }
 
 func getAccessToken(c *Context, w http.ResponseWriter, r *http.Request) {
-	r.ParseForm()
+	if err := r.ParseForm(); err != nil {
+		c.Err = model.NewAppError("getAccessToken", "api.oauth.get_access_token.bad_request.app_error", nil, "", http.StatusBadRequest)
+		return
+	}
 
 	code := r.FormValue("code")
 	refreshToken := r.FormValue("refresh_token")

server/i18n/en.json

@@ -2360,6 +2360,10 @@
     "id": "api.oauth.get_access_token.bad_grant.app_error",
     "translation": "invalid_request: Bad grant_type."
   },
+  {
+    "id": "api.oauth.get_access_token.bad_request.app_error",
+    "translation": "invalid_request: Bad request."
+  },
   {
     "id": "api.oauth.get_access_token.credentials.app_error",
     "translation": "invalid_client: Invalid client credentials."