Ensure beacon node generates the right eth2 spec

beacon_node/client/src/eth2_config.rs

@@ -20,6 +20,22 @@ impl Default for Eth2Config {
     }
 }
 
+impl Eth2Config {
+    pub fn mainnet() -> Self {
+        Self {
+            spec_constants: "mainnet".to_string(),
+            spec: ChainSpec::mainnet(),
+        }
+    }
+
+    pub fn minimal() -> Self {
+        Self {
+            spec_constants: "minimal".to_string(),
+            spec: ChainSpec::minimal(),
+        }
+    }
+}
+
 impl Eth2Config {
     /// Apply the following arguments to `self`, replacing values if they are specified in `args`.
     ///