Remove deleted resources and datasources from Terraform state on Read (all remaining services) (#346)

* Remove deleted resources and datasources from state on Read

* Simplify code

* Fix function description

Co-authored-by: Diogo Ferrão <diogo.ferrao@freiheit.com>

* Fix function description

Co-authored-by: Diogo Ferrão <diogo.ferrao@freiheit.com>

* Fix whitespace

---------

Co-authored-by: Diogo Ferrão <diogo.ferrao@freiheit.com>

stackit/internal/services/mongodbflex/instance/resource.go

@@ -3,6 +3,7 @@ package mongodbflex
 import (
 	"context"
 	"fmt"
+	"net/http"
 	"regexp"
 	"strings"
 
@@ -24,6 +25,7 @@ import (
 	"github.com/hashicorp/terraform-plugin-framework/resource/schema/stringplanmodifier"
 	"github.com/hashicorp/terraform-plugin-framework/types"
 	"github.com/stackitcloud/stackit-sdk-go/core/config"
+	"github.com/stackitcloud/stackit-sdk-go/core/oapierror"
 	"github.com/stackitcloud/stackit-sdk-go/services/mongodbflex"
 	"github.com/stackitcloud/stackit-sdk-go/services/mongodbflex/wait"
 )
@@ -384,6 +386,11 @@ func (r *instanceResource) Read(ctx context.Context, req resource.ReadRequest, r
 
 	instanceResp, err := r.client.GetInstance(ctx, projectId, instanceId).Execute()
 	if err != nil {
+		oapiErr, ok := err.(*oapierror.GenericOpenAPIError) //nolint:errorlint //complaining that error.As should be used to catch wrapped errors, but this error should not be wrapped
+		if ok && oapiErr.StatusCode == http.StatusNotFound {
+			resp.State.RemoveResource(ctx)
+			return
+		}
 		core.LogAndAddError(ctx, &resp.Diagnostics, "Error reading instance", err.Error())
 		return
 	}