Add upstream scheme support

Need to implement TCP and UDP upstream support.

Cargo.lock

@@ -96,9 +96,19 @@ dependencies = [
  "termcolor",
 ]
 
+[[package]]
+name = "form_urlencoded"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5fc25a87fa4fd2094bffb06925852034d90a17f0d1e05197d4956d3555752191"
+dependencies = [
+ "matches",
+ "percent-encoding",
+]
+
 [[package]]
 name = "fourth"
-version = "0.1.3"
+version = "0.1.4"
 dependencies = [
  "byte_string",
  "bytes 1.1.0",
@@ -110,6 +120,7 @@ dependencies = [
  "serde_yaml",
  "tls-parser",
  "tokio",
+ "url",
 ]
 
 [[package]]
@@ -241,6 +252,17 @@ dependencies = [
  "quick-error",
 ]
 
+[[package]]
+name = "idna"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "418a0a6fab821475f634efe3ccc45c013f742efe03d853e8d3355d5cb850ecf8"
+dependencies = [
+ "matches",
+ "unicode-bidi",
+ "unicode-normalization",
+]
+
 [[package]]
 name = "indexmap"
 version = "1.7.0"
@@ -318,6 +340,12 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "matches"
+version = "0.1.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a3e378b66a060d48947b590737b30a1be76706c8dd7b8ba0f2fe3989c68a853f"
+
 [[package]]
 name = "memchr"
 version = "2.4.1"
@@ -453,6 +481,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "percent-encoding"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d4fd5641d01c8f18a23da7b6fe29298ff4b55afcccdf78973b24cf3175fee32e"
+
 [[package]]
 name = "phf"
 version = "0.10.0"
@@ -721,6 +755,21 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "tinyvec"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f83b2a3d4d9091d0abd7eba4dc2710b1718583bd4d8992e2190720ea38f391f7"
+dependencies = [
+ "tinyvec_macros",
+]
+
+[[package]]
+name = "tinyvec_macros"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cda74da7e1a664f795bb1f8a87ec406fb89a02522cf6e50620d016add6dbbf5c"
+
 [[package]]
 name = "tls-parser"
 version = "0.11.0"
@@ -766,12 +815,39 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "unicode-bidi"
+version = "0.3.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a01404663e3db436ed2746d9fefef640d868edae3cceb81c3b8d5732fda678f"
+
+[[package]]
+name = "unicode-normalization"
+version = "0.1.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d54590932941a9e9266f0832deed84ebe1bf2e4c9e4a3554d393d18f5e854bf9"
+dependencies = [
+ "tinyvec",
+]
+
 [[package]]
 name = "unicode-xid"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8ccb82d61f80a663efe1f787a51b16b5a51e3314d6ac365b08639f52387b33f3"
 
+[[package]]
+name = "url"
+version = "2.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a507c383b2d33b5fc35d1861e77e6b383d158b2da5e14fe51b83dfedf6fd578c"
+dependencies = [
+ "form_urlencoded",
+ "idna",
+ "matches",
+ "percent-encoding",
+]
+
 [[package]]
 name = "version_check"
 version = "0.9.3"