[MM-37557] Move error out of client4 response (#18101)

* Return an error seperately from Response

* Remove BuildErrorResponse

* Drop Response.Error from model/client4.go

* Migrate require.Nil checks

* Migrate require.NotNil checks

* More manual fixes

* Move error check out of CheckOKStatus and CheckCreatedStatus

* Move error check out of CheckForbiddenStatus

* Move error check out of CheckUnauthorizedStatus

* Move error check out of CheckNotFoundStatus

* Move error check out of CheckBadRequestStatus

* Move error check out of CheckNotImplementedStatus and CheckRequestEntityTooLargeStatus

* Move error check out of CheckInternalErrorStatus

* Move error check out of CheckServiceUnavailableStatus

* Remove error check from checkHTTPStatus

* Remove remaining references to Response.Error

* Check previously unchecked errors

* Manually fix compile and linter errors

* Return error in CreateWebSocket methods

* Return error instead of *AppError in DoApi methods

* Manually fix bad replacments

* Conistently return Response and error

* Use err instead of seperate bool return value to indicate success

* Reduce ussage of model.AppError in web/oauth_test.go

* Remove client4.Must

* Check error in buf.ReadFrom

* Fix failing tests

api4/import_test.go

@@ -38,21 +38,21 @@ func TestListImports(t *testing.T) {
 			us.UserId = model.UploadNoUserID
 		}
 
-		u, resp := c.CreateUpload(us)
-		require.Nil(t, resp.Error)
+		u, _, err := c.CreateUpload(us)
+		require.NoError(t, err)
 		require.NotNil(t, u)
 
-		finfo, resp := c.UploadData(u.Id, file)
-		require.Nil(t, resp.Error)
+		finfo, _, err := c.UploadData(u.Id, file)
+		require.NoError(t, err)
 		require.NotNil(t, finfo)
 
 		return u.Id
 	}
 
 	t.Run("no permissions", func(t *testing.T) {
-		imports, resp := th.Client.ListImports()
-		require.NotNil(t, resp.Error)
-		require.Equal(t, "api.context.permissions.app_error", resp.Error.Id)
+		imports, _, err := th.Client.ListImports()
+		require.Error(t, err)
+		CheckErrorID(t, err, "api.context.permissions.app_error")
 		require.Nil(t, imports)
 	})
 
@@ -60,8 +60,8 @@ func TestListImports(t *testing.T) {
 	require.True(t, found)
 
 	th.TestForSystemAdminAndLocal(t, func(t *testing.T, c *model.Client4) {
-		imports, resp := c.ListImports()
-		require.Nil(t, resp.Error)
+		imports, _, err := c.ListImports()
+		require.NoError(t, err)
 		require.Empty(t, imports)
 	}, "no imports")
 
@@ -74,8 +74,8 @@ func TestListImports(t *testing.T) {
 		require.NoError(t, err)
 		f.Close()
 
-		imports, resp := c.ListImports()
-		require.Nil(t, resp.Error)
+		imports, _, err := c.ListImports()
+		require.NoError(t, err)
 		require.NotEmpty(t, imports)
 		require.Len(t, imports, 2)
 		require.Contains(t, imports, id+"_import_test.zip")
@@ -90,13 +90,13 @@ func TestListImports(t *testing.T) {
 
 		importDir := filepath.Join(dataDir, "import_new")
 
-		imports, resp := c.ListImports()
-		require.Nil(t, resp.Error)
+		imports, _, err := c.ListImports()
+		require.NoError(t, err)
 		require.Empty(t, imports)
 
 		id := uploadNewImport(c, t)
-		imports, resp = c.ListImports()
-		require.Nil(t, resp.Error)
+		imports, _, err = c.ListImports()
+		require.NoError(t, err)
 		require.NotEmpty(t, imports)
 		require.Len(t, imports, 1)
 		require.Equal(t, id+"_import_test.zip", imports[0])