miner auto-set mining key as node.seed

Author: ASuciuX

testnet/stacks-node/src/config.rs

@@ -833,7 +833,12 @@ impl Config {
         }
 
         let miner = match config_file.miner {
-            Some(miner) => miner.into_config_default(miner_default_config)?,
+            Some(mut miner) => {
+                if miner.mining_key.is_none() && !node.seed.is_empty() {
+                    miner.mining_key = Some(to_hex(&node.seed));
+                }
+                miner.into_config_default(miner_default_config)?
+            }
             None => miner_default_config,
         };
 
@@ -2546,6 +2551,13 @@ pub struct MinerConfigFile {
 
 impl MinerConfigFile {
     fn into_config_default(self, miner_default_config: MinerConfig) -> Result<MinerConfig, String> {
+        match &self.mining_key {
+            Some(_) => {}
+            None => {
+                panic!("mining key not set");
+            }
+        }
+
         let mining_key = self
             .mining_key
             .as_ref()