Refactor gree module

Cargo.lock

@@ -754,7 +754,6 @@ dependencies = [
  "rusqlite",
  "sha1",
  "sha2",
- "substring",
  "ureq",
  "urlencoding",
  "uuid",
@@ -2081,15 +2080,6 @@ version = "0.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"
 
-[[package]]
-name = "substring"
-version = "1.4.5"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "42ee6433ecef213b2e72f587ef64a2f5943e7cd16fbd82dbe8bc07486c534c86"
-dependencies = [
- "autocfg",
-]
-
 [[package]]
 name = "subtle"
 version = "2.6.1"