Cache network images by key other than URI

[halaei]

Introduction

There are a few reasons an image URI might not be the optimal choice for key of cached images:

1. The server URI may change in some applications.
2. The images may be in private storages and URLs can be temporary signed-urls.

Details

When creating an Image component, adding an optional key attribute that defaults to uri can improve caching ability in react native.

<Image
  source={{
    uri: 'https://example.com/image-1.jpg?signature=random',
    cacheKey: 'server/image-1.jpg'
  }}
/>

Discussion points

Just accept a key for caching.

PS: Here are some other image related notes:

1. Letting the user to choose/increase/decrease the maximum amount of space dedicated for caching will be fantastic. At the moment this value is constant (50MB I guess).
2. Supported sources are limited. It is almost impossible to write a native image component on top of react native to support your own image source, e.g. to show ID3 images of MP3 files over the network. Reading Java code, it doesn't seems it is extendible; it has a few hard coded switch cases in the code to detect type of source.
3. In android, it is better to cache images in application's cache directory rather than it's data directory.