First implementation of K2V (#293)

**Specification:**

View spec at [this URL](https://git.deuxfleurs.fr/Deuxfleurs/garage/src/branch/k2v/doc/drafts/k2v-spec.md)

- [x] Specify the structure of K2V triples
- [x] Specify the DVVS format used for causality detection
- [x] Specify the K2V index (just a counter of number of values per partition key)
- [x] Specify single-item endpoints: ReadItem, InsertItem, DeleteItem
- [x] Specify index endpoint: ReadIndex
- [x] Specify multi-item endpoints: InsertBatch, ReadBatch, DeleteBatch
- [x] Move to JSON objects instead of tuples
- [x] Specify endpoints for polling for updates on single values (PollItem)

**Implementation:**

- [x] Table for K2V items, causal contexts
- [x] Indexing mechanism and table for K2V index
- [x] Make API handlers a bit more generic
- [x] K2V API endpoint
- [x] K2V API router
- [x] ReadItem
- [x] InsertItem
- [x] DeleteItem
- [x] PollItem
- [x] ReadIndex
- [x] InsertBatch
- [x] ReadBatch
- [x] DeleteBatch

**Testing:**

- [x] Just a simple Python script that does some requests to check visually that things are going right (does not contain parsing of results or assertions on returned values)
- [x] Actual tests:
  - [x] Adapt testing framework
  - [x] Simple test with InsertItem + ReadItem
  - [x] Test with several Insert/Read/DeleteItem + ReadIndex
  - [x] Test all combinations of return formats for ReadItem
  - [x] Test with ReadBatch, InsertBatch, DeleteBatch
  - [x] Test with PollItem
  - [x] Test error codes
- [ ] Fix most broken stuff
  - [x] test PollItem broken randomly
  - [x] when invalid causality tokens are given, errors should be 4xx not 5xx

**Improvements:**

- [x] Descending range queries
  - [x] Specify
  - [x] Implement
  - [x] Add test
- [x] Batch updates to index counter
- [x] Put K2V behind `k2v` feature flag

Co-authored-by: Alex Auvolat <alex@adnab.me>
Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/293
Co-authored-by: Alex <alex@adnab.me>
Co-committed-by: Alex <alex@adnab.me>

1 files changed, 0 insertions, 31 deletions

diff --git a/src/garage/tests/simple.rs b/src/garage/tests/simple.rs
deleted file mode 100644
index f54ae9ac..00000000
--- a/src/garage/tests/simple.rs
+++ /dev/null
@@ -1,31 +0,0 @@
-use crate::common;
-
-#[tokio::test]
-async fn test_simple() {
-	use aws_sdk_s3::types::ByteStream;
-
-	let ctx = common::context();
-	let bucket = ctx.create_bucket("test-simple");
-
-	let data = ByteStream::from_static(b"Hello world!");
-
-	ctx.client
-		.put_object()
-		.bucket(&bucket)
-		.key("test")
-		.body(data)
-		.send()
-		.await
-		.unwrap();
-
-	let res = ctx
-		.client
-		.get_object()
-		.bucket(&bucket)
-		.key("test")
-		.send()
-		.await
-		.unwrap();
-
-	assert_bytes_eq!(res.body, b"Hello world!");
-}