Can specify environment variables in client configuration

Cargo.lock

@@ -421,6 +421,7 @@ dependencies = [
  "futures-util",
  "include_dir",
  "jwt-simple",
+ "lazy-regex",
  "log",
  "mime_guess",
  "rand",
@@ -1211,6 +1212,29 @@ version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d4345964bb142484797b161f473a503a434de77149dd8c7427788c6e13379388"
 
+[[package]]
+name = "lazy-regex"
+version = "2.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b6b12f2eb6ed7d39405c5eb25a034b4c106a9ad87a6d9be3298de6c5f32fd57d"
+dependencies = [
+ "lazy-regex-proc_macros",
+ "once_cell",
+ "regex",
+]
+
+[[package]]
+name = "lazy-regex-proc_macros"
+version = "2.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f2496e5264069bc726ccf37eb76b9cd89406ae110d836c3f76729f99c8a23293"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "regex",
+ "syn",
+]
+
 [[package]]
 name = "lazy_static"
 version = "1.4.0"