redap_tasks: introduce grpc definitions (#9359)

### Related


* Part of [redap #276
](rerun-io/dataplatform#276)

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* Closes #1234
* Part of #1337
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### What

This PR introduces gRPC definitions for the service that will enable
interaction with redap persistent tasks. See [redap #276
](rerun-io/dataplatform#276).

Author: andrea-reale

crates/store/re_protos/proto/rerun/v1alpha1/tasks.proto

@@ -0,0 +1,45 @@
+syntax = "proto3";
+
+package rerun.redap_tasks.v1alpha1;
+
+import "rerun/v1alpha1/common.proto";
+
+// `TasksService` is the service for submitting and querying persistent redap tasks.
+service TasksService {
+  // Submit new tasks
+  rpc SubmitTasks(SubmitTasksRequest) returns (SubmitTasksResponse);
+  // Query the status of submitted tasks
+  rpc Query(QueryRequest) returns (QueryResponse);
+}
+
+message SubmitTasksRequest {
+  repeated Task tasks = 1;
+}
+
+// `SubmitTaskResponse` contains, for each submitted task
+// its submission outcome, encoded as a `RecordBatch`
+message SubmitTasksResponse {
+  rerun.common.v1alpha1.DataframePart data = 1;
+}
+
+// A task is a unit of work that can be submitted to the system
+message Task {
+  // Unique identifier for the task
+  string task_id = 1;
+  // Type of the task
+  string task_type = 2;
+  // Task-type dependant data necessary to de-serialize the task
+  bytes task_data = 3;
+}
+
+// `QueryRequest` is the request message for querying tasks status
+message QueryRequest {
+  // Empty queries for all tasks if the server allows it.
+  repeated string task_ids = 2;
+}
+
+// `QueryResponse` is the response message for querying tasks status
+// encoded as a record batch
+message QueryResponse {
+  rerun.common.v1alpha1.DataframePart data = 1;
+}

crates/store/re_protos/src/lib.rs

@@ -42,6 +42,9 @@ mod v1alpha1 {
 
     #[path = "./rerun.frontend.v1alpha1.rs"]
     pub mod rerun_frontend_v1alpha1;
+
+    #[path = "./rerun.redap_tasks.v1alpha1.rs"]
+    pub mod rerun_redap_tasks_v1alpha1;
 }
 
 pub mod common {
@@ -110,6 +113,12 @@ pub mod sdk_comms {
     }
 }
 
+pub mod redap_tasks {
+    pub mod v1alpha1 {
+        pub use crate::v1alpha1::rerun_redap_tasks_v1alpha1::*;
+    }
+}
+
 #[derive(Debug, thiserror::Error)]
 pub enum TypeConversionError {
     #[error("missing required field: {package_name}.{type_name}.{field_name}")]