Secrets: Add fallback to secrets kvstore plugin (#54056)

* Add fallback to secrets kvstore plugin

* Fix linter issues

* Fix linter issues

* Add deletion error to bool to fake secrets kvstore

* Add fallback to fake secrets kvstore

* Fix fake secrets kvstore fallback setter

* Use Key on Item message for secrets manager protobuf

* Add clarifying comment about fallback

pkg/plugins/backendplugin/secretsmanagerplugin/secretsmanager.proto

@@ -9,6 +9,11 @@ message Key {
     string type = 3;
 }
 
+message Item {
+    Key key = 1;
+    string value = 2;
+}
+
 message GetSecretRequest {
     Key keyDescriptor = 1;
 }
@@ -16,7 +21,7 @@ message GetSecretRequest {
 message GetSecretResponse {
     string userFriendlyError = 1;
     string decryptedValue = 2;
-    bool exists = 3;  
+    bool exists = 3;
 }
 
 message SetSecretRequest {
@@ -46,6 +51,14 @@ message ListSecretsResponse {
     repeated Key keys = 2;
 }
 
+message GetAllSecretsRequest {
+}
+
+message GetAllSecretsResponse {
+    string userFriendlyError = 1;
+    repeated Item items = 2;
+}
+
 message RenameSecretRequest {
     Key keyDescriptor = 1;
     string newNamespace = 2;
@@ -61,4 +74,5 @@ service SecretsManager {
     rpc DeleteSecret(DeleteSecretRequest) returns (DeleteSecretResponse);
     rpc ListSecrets(ListSecretsRequest) returns (ListSecretsResponse);
     rpc RenameSecret(RenameSecretRequest) returns (RenameSecretResponse);
-}
+    rpc GetAllSecrets(GetAllSecretsRequest) returns (GetAllSecretsResponse);
+}