remove block fork guessing/inference from REST JSON decoding (#6552)

* remove block fork guessing/inference from REST JSON decoding

* use template to avoid repetitive per-fork code

* consolidate RestPublishedSignedBeaconBlock and RestPublishedSignedBlockContents parsing fork handling

AllTests-mainnet.md

@@ -821,10 +821,9 @@ OK: 1/1 Fail: 0/1 Skip: 0/1
 + DenebSignedBlockContents decoding                                                          OK
 + KzgCommitment                                                                              OK
 + KzgProof                                                                                   OK
-+ RestPublishedSignedBlockContents decoding                                                  OK
 + Validator pubkey hack                                                                      OK
 ```
-OK: 6/6 Fail: 0/6 Skip: 0/6
+OK: 5/5 Fail: 0/5 Skip: 0/5
 ## Remove keystore testing suite
 ```diff
 + Many remotes                                                                               OK
@@ -1126,4 +1125,4 @@ OK: 2/2 Fail: 0/2 Skip: 0/2
 OK: 9/9 Fail: 0/9 Skip: 0/9
 
 ---TOTAL---
-OK: 763/768 Fail: 0/768 Skip: 5/768
+OK: 762/767 Fail: 0/767 Skip: 5/767

beacon_chain/rpc/rest_beacon_api.nim

@@ -901,10 +901,23 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
           return RestApiResponse.jsonError(Http400, EmptyRequestBodyError)
         let
           body = contentBody.get()
-          version = request.headers.getString("eth-consensus-version")
-          restBlock = decodeBody(
-            RestPublishedSignedBlockContents, body, version).valueOr:
-              return RestApiResponse.jsonError(error)
+          currentEpochFork =
+            node.dag.cfg.consensusForkAtEpoch(node.currentSlot().epoch())
+          rawVersion = request.headers.getString("eth-consensus-version")
+
+          # The V1 endpoint doesn't require the version to be specified but the
+          # only fork which works is the current gossip fork. Either it can use
+          # and broadcast a block in that fork or that broadcast will not prove
+          # useful anyway, so allow it to fail at the decoding stage.
+          version =
+            if rawVersion == "":
+              currentEpochFork.toString
+            else:
+              rawVersion
+
+        let restBlock = decodeBody(
+          RestPublishedSignedBlockContents, body, version).valueOr:
+            return RestApiResponse.jsonError(error)
 
         withForkyBlck(restBlock):
           if restBlock.kind != node.dag.cfg.consensusForkAtEpoch(
@@ -1047,9 +1060,19 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
     let
       currentEpochFork =
         node.dag.cfg.consensusForkAtEpoch(node.currentSlot().epoch())
-      version = request.headers.getString("eth-consensus-version")
+      rawVersion = request.headers.getString("eth-consensus-version")
       body = contentBody.get()
 
+      # The V1 endpoint doesn't require the version to be specified but the
+      # only fork which works is the current gossip fork. Either it can use
+      # and broadcast a block in that fork or that broadcast will not prove
+      # useful anyway, so allow it to fail at the decoding stage.
+      version =
+        if rawVersion == "":
+          currentEpochFork.toString
+        else:
+          rawVersion
+
     if (body.contentType == OctetStreamMediaType) and
        (currentEpochFork.toString != version):
       return RestApiResponse.jsonError(Http400, BlockIncorrectFork)