Per-API Key Caches (#74)

* cache racing start in place

* additional test

* clean up debug logs

* cleanup from self-review of PR

* clean up annotations

* test created

* independant storages

* changes from self-review of PR

* make suffix required in the persistant stores

* fix up tests

* test for local storage

* test for index

* fix test typescript error

Author: aarsilv

docs/js-client-sdk.chromestorageasyncstore._constructor_.md

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+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [@eppo/js-client-sdk](./js-client-sdk.md) &gt; [ChromeStorageEngine](./js-client-sdk.chromestorageengine.md) &gt; [(constructor)](./js-client-sdk.chromestorageengine._constructor_.md)
+
+## ChromeStorageEngine.(constructor)
+
+Constructs a new instance of the `ChromeStorageEngine` class
+
+**Signature:**
+
+```typescript
+constructor(storageArea: chrome.storage.StorageArea);
+```
+
+## Parameters
+
+|  Parameter | Type | Description |
+|  --- | --- | --- |
+|  storageArea | chrome.storage.StorageArea |  |
+

docs/js-client-sdk.chromestorageasyncstore.getentries.md

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+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [@eppo/js-client-sdk](./js-client-sdk.md) &gt; [ChromeStorageEngine](./js-client-sdk.chromestorageengine.md) &gt; [getContentsJsonString](./js-client-sdk.chromestorageengine.getcontentsjsonstring.md)
+
+## ChromeStorageEngine.getContentsJsonString property
+
+**Signature:**
+
+```typescript
+getContentsJsonString: () => Promise<string | null>;
+```

docs/js-client-sdk.chromestorageasyncstore.isexpired.md

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+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [@eppo/js-client-sdk](./js-client-sdk.md) &gt; [ChromeStorageEngine](./js-client-sdk.chromestorageengine.md) &gt; [getMetaJsonString](./js-client-sdk.chromestorageengine.getmetajsonstring.md)
+
+## ChromeStorageEngine.getMetaJsonString property
+
+**Signature:**
+
+```typescript
+getMetaJsonString: () => Promise<string | null>;
+```

docs/js-client-sdk.chromestorageasyncstore.isinitialized.md

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+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [@eppo/js-client-sdk](./js-client-sdk.md) &gt; [ChromeStorageEngine](./js-client-sdk.chromestorageengine.md)
+
+## ChromeStorageEngine class
+
+Chrome storage implementation of a string-valued store for storing a configuration and its metadata.
+
+This serializes the entire configuration object into a string and then stores it to a single key within the object for another single top-level key. Same with metadata about the store (e.g., when it was last updated).
+
+**Signature:**
+
+```typescript
+export declare class ChromeStorageEngine implements IStringStorageEngine 
+```
+**Implements:** IStringStorageEngine
+
+## Constructors
+
+|  Constructor | Modifiers | Description |
+|  --- | --- | --- |
+|  [(constructor)(storageArea)](./js-client-sdk.chromestorageengine._constructor_.md) |  | Constructs a new instance of the <code>ChromeStorageEngine</code> class |
+
+## Properties
+
+|  Property | Modifiers | Type | Description |
+|  --- | --- | --- | --- |
+|  [getContentsJsonString](./js-client-sdk.chromestorageengine.getcontentsjsonstring.md) |  | () =&gt; Promise&lt;string \| null&gt; |  |
+|  [getMetaJsonString](./js-client-sdk.chromestorageengine.getmetajsonstring.md) |  | () =&gt; Promise&lt;string \| null&gt; |  |
+|  [setContentsJsonString](./js-client-sdk.chromestorageengine.setcontentsjsonstring.md) |  | (configurationJsonString: string) =&gt; Promise&lt;void&gt; |  |
+|  [setMetaJsonString](./js-client-sdk.chromestorageengine.setmetajsonstring.md) |  | (metaJsonString: string) =&gt; Promise&lt;void&gt; |  |
+