Adding a possibility to have a custom cache-key generator.

[jeroenbach]

In our API calls we pass a languageid & siteid as header data, which will give us different results. For this it would be handy for us to allow passing a custom cachekey generator with the options.

Do you agree with this idea? If yes, then we can also create a Pull Request with this change if you don't have time to add it?

In throttleAdapterEnhancer & cacheAdapterEnhancer:

var customCacheKey = options.cacheKeyGenerator && options.cacheKeyGenerator(config, buildSortedURL(url, params, paramsSerializer));
var index_1 = customCacheKey || buildSortedURL(url, params, paramsSerializer);

and then in the calling method we can pass the cacheKeyGenerator to the options.

cacheAdapterEnhancer(axios.defaults.adapter, { cacheKeyGenerator: (config, originalKey) => { /*custom logic*/}});

[kuitos]

cool, feel free to submit a pr