Support SSZ request body for POST /beacon/blinded_blocks endpoints (v1 & v2) (#4504)

## Issue Addressed

#4262 

## Proposed Changes

add SSZ support in request body for POST /beacon/blinded_blocks endpoints (v1 & v2)

## Additional Info

beacon_node/http_api/tests/broadcast_validation_tests.rs

@@ -851,6 +851,49 @@ pub async fn blinded_gossip_full_pass() {
         .block_is_known_to_fork_choice(&block.canonical_root()));
 }
 
+// This test checks that a block that is valid from both a gossip and consensus perspective is accepted when using `broadcast_validation=gossip`.
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+pub async fn blinded_gossip_full_pass_ssz() {
+    /* this test targets gossip-level validation */
+    let validation_level: Option<BroadcastValidation> = Some(BroadcastValidation::Gossip);
+
+    // Validator count needs to be at least 32 or proposer boost gets set to 0 when computing
+    // `validator_count // 32`.
+    let validator_count = 64;
+    let num_initial: u64 = 31;
+    let tester = InteractiveTester::<E>::new(None, validator_count).await;
+
+    // Create some chain depth.
+    tester.harness.advance_slot();
+    tester
+        .harness
+        .extend_chain(
+            num_initial as usize,
+            BlockStrategy::OnCanonicalHead,
+            AttestationStrategy::AllValidators,
+        )
+        .await;
+    tester.harness.advance_slot();
+
+    let slot_a = Slot::new(num_initial);
+    let slot_b = slot_a + 1;
+
+    let state_a = tester.harness.get_current_state();
+    let (block, _): (SignedBlindedBeaconBlock<E>, _) =
+        tester.harness.make_blinded_block(state_a, slot_b).await;
+
+    let response: Result<(), eth2::Error> = tester
+        .client
+        .post_beacon_blinded_blocks_v2_ssz(&block, validation_level)
+        .await;
+
+    assert!(response.is_ok());
+    assert!(tester
+        .harness
+        .chain
+        .block_is_known_to_fork_choice(&block.canonical_root()));
+}
+
 /// This test checks that a block that is **invalid** from a gossip perspective gets rejected when using `broadcast_validation=consensus`.
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 pub async fn blinded_consensus_invalid() {