Implement the caching mechanism for the publisher restrictions in TCData class

[sevriugin]

Description

To implement the caching mechanism we introduce in the IAB TCF cmpapi library two new classes: CacheBucket and Cache .

The CacheBucket class implements actual caching mechanism and provides get method that accepts cache key, recalculation function and recalculation functions parameters as arguments. The CacheBucket class also has a name property.

The Cache class implements a collection (map) of CacheBucket objects with several simple methods including the getBucket method to get/create CacheBucket using name string.

We need this two level structure to separate caching for two classes TCData and InAppTCData .

We use Cache class to create restrictionsCache in CmpApiModel singleton class that "... acts much like a global state or database, where CmpApi sets data and Commands read the data".

The TCData class uses restrictionsCache to get cache bucket using class name

const bucket = CmpApiModel.restrictionsCache.getBucket(this.constructor.name);

Now the publisher restrictions could be extracted from the CacheBucket or recalculated if consent string value is changed

const restrictions = bucket.get(this.tcString, this.createRestrictions.bind(this), tcModel.publisherRestrictions );

Summary of changes

• CacheBucket class implemented;
• Cache class implemented;
• Update CmpApiModel class (singleton) to add restrictionsCache parameter;
• Update TCData class to use restrictions cache from the singleton object CmpApiModel;
• Add unit and integrations tests.