Kiln mev boost (#3062)

## Issue Addressed

MEV boost compatibility

## Proposed Changes

See #2987

## Additional Info

This is blocked on the stabilization of a couple specs, [here](https://github.com/ethereum/beacon-APIs/pull/194) and [here](https://github.com/flashbots/mev-boost/pull/20).

Additional TODO's and outstanding questions

- [ ] MEV boost JWT Auth
- [ ] Will `builder_proposeBlindedBlock` return the revealed payload for the BN to propogate
- [ ] Should we remove `private-tx-proposals` flag and communicate BN <> VC with blinded blocks by default once these endpoints enter the beacon-API's repo? This simplifies merge transition logic. 

Co-authored-by: realbigsean <seananderson33@gmail.com>
Co-authored-by: realbigsean <sean@sigmaprime.io>

beacon_node/execution_layer/src/engine_api.rs

@@ -1,18 +1,21 @@
+use crate::engines::ForkChoiceState;
 use async_trait::async_trait;
 use eth1::http::RpcError;
+pub use json_structures::TransitionConfigurationV1;
 use reqwest::StatusCode;
 use serde::{Deserialize, Serialize};
-
-pub const LATEST_TAG: &str = "latest";
-
-use crate::engines::ForkChoiceState;
-pub use json_structures::TransitionConfigurationV1;
-pub use types::{Address, EthSpec, ExecutionBlockHash, ExecutionPayload, Hash256, Uint256};
+use slog::Logger;
+pub use types::{
+    Address, EthSpec, ExecutionBlockHash, ExecutionPayload, ExecutionPayloadHeader, Hash256,
+    Uint256,
+};
 
 pub mod auth;
 pub mod http;
 pub mod json_structures;
 
+pub const LATEST_TAG: &str = "latest";
+
 pub type PayloadId = [u8; 8];
 
 #[derive(Debug)]
@@ -24,7 +27,10 @@ pub enum Error {
     InvalidExecutePayloadResponse(&'static str),
     JsonRpc(RpcError),
     Json(serde_json::Error),
-    ServerMessage { code: i64, message: String },
+    ServerMessage {
+        code: i64,
+        message: String,
+    },
     Eip155Failure,
     IsSyncing,
     ExecutionBlockNotFound(ExecutionBlockHash),
@@ -32,6 +38,14 @@ pub enum Error {
     ParentHashEqualsBlockHash(ExecutionBlockHash),
     PayloadIdUnavailable,
     TransitionConfigurationMismatch,
+    PayloadConversionLogicFlaw,
+    InvalidBuilderQuery,
+    MissingPayloadId {
+        parent_hash: ExecutionBlockHash,
+        timestamp: u64,
+        prev_randao: Hash256,
+        suggested_fee_recipient: Address,
+    },
 }
 
 impl From<reqwest::Error> for Error {
@@ -59,41 +73,17 @@ impl From<auth::Error> for Error {
     }
 }
 
-/// A generic interface for an execution engine API.
+pub struct EngineApi;
+pub struct BuilderApi;
+
 #[async_trait]
-pub trait EngineApi {
-    async fn upcheck(&self) -> Result<(), Error>;
-
-    async fn get_block_by_number<'a>(
-        &self,
-        block_by_number: BlockByNumberQuery<'a>,
-    ) -> Result<Option<ExecutionBlock>, Error>;
-
-    async fn get_block_by_hash<'a>(
-        &self,
-        block_hash: ExecutionBlockHash,
-    ) -> Result<Option<ExecutionBlock>, Error>;
-
-    async fn new_payload_v1<T: EthSpec>(
-        &self,
-        execution_payload: ExecutionPayload<T>,
-    ) -> Result<PayloadStatusV1, Error>;
-
-    async fn get_payload_v1<T: EthSpec>(
-        &self,
-        payload_id: PayloadId,
-    ) -> Result<ExecutionPayload<T>, Error>;
-
-    async fn forkchoice_updated_v1(
+pub trait Builder {
+    async fn notify_forkchoice_updated(
         &self,
         forkchoice_state: ForkChoiceState,
         payload_attributes: Option<PayloadAttributes>,
+        log: &Logger,
     ) -> Result<ForkchoiceUpdatedResponse, Error>;
-
-    async fn exchange_transition_configuration_v1(
-        &self,
-        transition_configuration: TransitionConfigurationV1,
-    ) -> Result<TransitionConfigurationV1, Error>;
 }
 
 #[derive(Clone, Copy, Debug, PartialEq)]
@@ -142,3 +132,17 @@ pub struct ForkchoiceUpdatedResponse {
     pub payload_status: PayloadStatusV1,
     pub payload_id: Option<PayloadId>,
 }
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum ProposeBlindedBlockResponseStatus {
+    Valid,
+    Invalid,
+    Syncing,
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct ProposeBlindedBlockResponse {
+    pub status: ProposeBlindedBlockResponseStatus,
+    pub latest_valid_hash: Option<Hash256>,
+    pub validation_error: Option<String>,
+}