[DEV-1658] Support projection v2 engine

kurrentdb/protos/projections.proto

@@ -28,6 +28,7 @@ message CreateReq {
 			Continuous continuous = 3;
 		}
 		string query = 4;
+		int32 engine_version = 5;
 
 		message Transient {
 			string name = 1;

kurrentdb/src/event_store/generated/projections.rs

@@ -10,6 +10,8 @@ pub mod create_req {
     pub struct Options {
         #[prost(string, tag = "4")]
         pub query: ::prost::alloc::string::String,
+        #[prost(int32, tag = "5")]
+        pub engine_version: i32,
         #[prost(oneof = "options::Mode", tags = "1, 2, 3")]
         pub mode: ::core::option::Option<options::Mode>,
     }

kurrentdb/src/options/projections.rs

@@ -1,10 +1,30 @@
 use kurrentdb_macros::options;
 
+/// Selects which projection engine the server should use when creating a
+/// continuous projection. `V1` is the default and is supported by every server
+/// version. `V2` requires a server that supports the next-generation engine.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub enum ProjectionEngineVersion {
+    #[default]
+    V1,
+    V2,
+}
+
+impl ProjectionEngineVersion {
+    pub(crate) fn as_i32(self) -> i32 {
+        match self {
+            ProjectionEngineVersion::V1 => 1,
+            ProjectionEngineVersion::V2 => 2,
+        }
+    }
+}
+
 options! {
     #[derive(Clone, Default)]
     pub struct CreateProjectionOptions {
         pub(crate) track_emitted_streams: bool,
         pub(crate) emit: bool,
+        pub(crate) engine_version: ProjectionEngineVersion,
     }
 }
 
@@ -23,6 +43,13 @@ impl CreateProjectionOptions {
     pub fn emit(self, emit: bool) -> Self {
         Self { emit, ..self }
     }
+
+    pub fn engine_version(self, engine_version: ProjectionEngineVersion) -> Self {
+        Self {
+            engine_version,
+            ..self
+        }
+    }
 }
 
 options! {

kurrentdb/src/projection_client.rs

@@ -74,6 +74,7 @@ impl ProjectionClient {
             options,
             projections::create_req::Options {
                 query: query.clone(),
+                engine_version: options.engine_version.as_i32(),
                 mode: Some(projections::create_req::options::Mode::Continuous(
                     projections::create_req::options::Continuous {
                         name: name.as_ref().to_string(),