Support for PostObject (#222)

Add support for [PostObject](https://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectPOST.html)

- [x] routing PostObject properly
- [x] parsing multipart body
- [x] validating signature
- [x] validating policy
- [x] validating content length
- [x] actually saving data

Co-authored-by: trinity-1686a <trinity@deuxfleurs.fr>
Co-authored-by: Trinity Pointard <trinity.pointard@gmail.com>
Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/222
Reviewed-by: Alex <alex@adnab.me>
Co-authored-by: trinity-1686a <trinity.pointard@gmail.com>
Co-committed-by: trinity-1686a <trinity.pointard@gmail.com>

Cargo.lock

@@ -469,6 +469,15 @@ version = "1.6.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
 
+[[package]]
+name = "encoding_rs"
+version = "0.8.30"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7896dc8abb250ffdda33912550faa54c88ec8b998dec0b2c55ab224921ce11df"
+dependencies = [
+ "cfg-if",
+]
+
 [[package]]
 name = "env_logger"
 version = "0.7.1"
@@ -690,6 +699,7 @@ dependencies = [
  "chrono",
  "crypto-mac 0.10.1",
  "err-derive 0.3.0",
+ "form_urlencoded",
  "futures",
  "futures-util",
  "garage_model 0.6.0",
@@ -704,6 +714,7 @@ dependencies = [
  "idna",
  "log",
  "md-5",
+ "multer",
  "nom",
  "percent-encoding",
  "pin-project",
@@ -711,6 +722,7 @@ dependencies = [
  "roxmltree",
  "serde",
  "serde_bytes",
+ "serde_json",
  "sha2",
  "tokio",
  "url",
@@ -1314,6 +1326,12 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "mime"
+version = "0.3.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2a60c7ce501c71e03a9c9c0d35b861413ae925bd979cc7a4e30d060069aaac8d"
+
 [[package]]
 name = "minimal-lexical"
 version = "0.2.1"
@@ -1342,6 +1360,24 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "multer"
+version = "2.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5f8f35e687561d5c1667590911e6698a8cb714a134a7505718a182e7bc9d3836"
+dependencies = [
+ "bytes 1.1.0",
+ "encoding_rs",
+ "futures-util",
+ "http",
+ "httparse",
+ "log",
+ "memchr",
+ "mime",
+ "spin 0.9.2",
+ "version_check",
+]
+
 [[package]]
 name = "netapp"
 version = "0.3.0"
@@ -1670,7 +1706,7 @@ dependencies = [
  "cc",
  "libc",
  "once_cell",
- "spin",
+ "spin 0.5.2",
  "untrusted",
  "web-sys",
  "winapi",
@@ -1933,6 +1969,12 @@ version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"
 
+[[package]]
+name = "spin"
+version = "0.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "511254be0c5bcf062b019a6c89c01a664aa359ded62f78aa72c6fc137c0590e5"
+
 [[package]]
 name = "static_init"
 version = "1.0.2"