feat(frontier): accept stripe billing webhook

Signed-off-by: Kush Sharma <[email protected]>

raystack/frontier/v1beta1/admin.proto

@@ -337,6 +337,19 @@ service AdminService {
     };
   }
 
+  // Incoming Webhooks
+  rpc AcceptBillingWebhook(AcceptBillingWebhookRequest) returns (AcceptBillingWebhookResponse) {
+    option (google.api.http) = {
+      post: "/v1beta1/admin/billing/webhook/{provider}",
+      body: "body"
+    };
+    option (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_operation) = {
+      tags: "Webhook";
+      summary: "Accept Billing webhook";
+      description: "Accepts a Billing webhook and processes it.";
+    };
+  }
+
   // Usage
   rpc RevertBillingUsage(RevertBillingUsageRequest) returns (RevertBillingUsageResponse) {
     option (google.api.http) = {
@@ -711,3 +724,10 @@ message ListWebhooksRequest {}
 message ListWebhooksResponse {
   repeated Webhook webhooks = 1;
 }
+
+message AcceptBillingWebhookRequest {
+  string provider = 1 [(validate.rules).string = {min_len: 1}];
+  google.protobuf.Struct body = 2;
+}
+
+message AcceptBillingWebhookResponse {}