✨ feat(cli): add config file support

- load configuration from a file
- use config crate for config loading
- allow overriding config with environment variables
- set default credential path
- fix error handling for config loading

Cargo.lock

@@ -240,6 +240,19 @@ version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b05b61dc5112cbb17e4b6cd61790d9845d13888356391624cbe7e41efeac1e75"
 
+[[package]]
+name = "config"
+version = "0.15.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "180e549344080374f9b32ed41bf3b6b57885ff6a289367b3dbc10eea8acc1918"
+dependencies = [
+ "pathdiff",
+ "serde_core",
+ "serde_json",
+ "toml",
+ "winnow",
+]
+
 [[package]]
 name = "core-foundation"
 version = "0.10.1"
@@ -263,6 +276,7 @@ dependencies = [
  "chrono",
  "clap",
  "clap-verbosity-flag",
+ "config",
  "env_logger",
  "google-gmail1",
  "log",
@@ -1017,6 +1031,12 @@ version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d05e27ee213611ffe7d6348b942e8f942b37114c00cc03cec254295a4a17852e"
 
+[[package]]
+name = "pathdiff"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df94ce210e5bc13cb6651479fa48d14f601d9858cfe0467f43ae157023b938d3"
+
 [[package]]
 name = "percent-encoding"
 version = "2.3.2"
@@ -1964,6 +1984,9 @@ name = "winnow"
 version = "0.7.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "21a0236b59786fed61e2a80582dd500fe61f18b5dca67a4a067d0bc9039339cf"
+dependencies = [
+ "memchr",
+]
 
 [[package]]
 name = "writeable"