Extend Optable Targeting API request forming with additional parameters

[ValentinPostindustria]

Motivation

Feature completeness of the Targeting API support in the SDK.

Details

The current implementation does not allow passing arbitrary identifiers and other params - thus is not complete to spec, documented here: https://docs.optable.co/optable-documentation/admin/real-time-api/api-integrations-guide/optable-targeting-api

The Targeting Request construction should accept arbitrary IDs as defined per spec and privacy parameters.
By default consent data including strings should be obtained from the standard IAB-defined locations in the UserDefaults.

Objective

1. Implement the prerequisite generic API call parametrization Rework Optable Real-time APIs configuration and request forming #33.
2. Extend Targeting interface to accept additional parameters (s.a. various IDs and privacy params)
3. Rework request construction
4. Improve response processing into a convenient data structure to be used with the Prebid SDK - this is likely to be the primary enrichment target.
5. Implement unit test coverage for the request forming and ideally against the mock server to check response parsing if any.
6. Update the example app to configure a Targeting call and enrich the Prebid SDK call.

[ValentinPostindustria]

Identifiers

Please extend the identify interface. gaid: can stay as boolean as it is obtained automatically, but instead of just email and ppid - it should take an identifiers: HashMap<String,String> param. A HashMap of prefixes as keys and identifiers as values. email can be one of them it will have e as a prefix, but ppids are not limited to c - they can have a prefix c, but also in a range from c1 to c19. Read a chapter on identifer types and prefixes - these same prefixes are used in forming the request to Identify so you will just use the keys as needed from this HashMap (these same identifiers can also be sent to Targeting API, but Targeting can use solely passport containing a visitor id after identify has linked these to the visitor id. Make sure to document this method well and add links to the above.