Introducing DeltaReader (#7)

* Get largest test and tests simplifications

* More tests and more renaming

* Get prev!

* Implement the rest without testing

* Clean up

* Minor comments clean up

* Add tests for get

* More test for empty delta reader

* More tests and use own type alias

* Adding more tests for collect in range

* Adding proptest for more iterator related things

* Move PaginatedResponse from lib to cache

src/cache/cache_db.rs

@@ -4,7 +4,7 @@ use std::sync::Mutex;
 
 use crate::cache::cache_container::CacheContainer;
 use crate::cache::change_set::ChangeSet;
-use crate::cache::SnapshotId;
+use crate::cache::{PaginatedResponse, SnapshotId};
 use crate::iterator::ScanDirection;
 use crate::schema::KeyDecoder;
 use crate::{
@@ -19,16 +19,6 @@ pub struct CacheDb {
     db: ReadOnlyLock<CacheContainer>,
 }
 
-/// Response for a paginated query which also includes the "next" key to pass
-#[derive(Debug)]
-pub struct PaginatedResponse<S: Schema> {
-    /// A vector of storage keys and their values
-    pub key_value: Vec<(S::Key, S::Value)>,
-    /// Key indicating the first key after the final pair from key_value.
-    /// Meant to be passed in in subsequent queries
-    pub next: Option<S::Key>,
-}
-
 impl CacheDb {
     /// Create new [`CacheDb`] pointing to given [`CacheContainer`]
     pub fn new(id: SnapshotId, cache_container: ReadOnlyLock<CacheContainer>) -> Self {