Use volumes to share sshkey and authorized keys instead of copying and add build time variables to docker-compose

docker-compose-generator/src/Properties/launchSettings.json

@@ -4,6 +4,7 @@
       "commandName": "Project",
       "commandLineArgs": "pregen",
       "environmentVariables": {
+        "BTCPAY_HOST_SSHKEYFILE": "test.rsa",
         "BTCPAYGEN_LIGHTNING": "clightning",
         "BTCPAYGEN_CRYPTO4": "ftc",
         "BTCPAYGEN_CRYPTO3": "btg",
@@ -13,4 +14,4 @@
       }
     }
   }
-}
+}