Better document the relationship between the mapping and build stages

[yolile]

Some aspects of the mapping process could inform the build stage of the OCDS implementation. For example, during the mapping process, you should map:

• The release.date and release.id fields. If these fields are not part of the source system, which is normally the case, then you need to think about how you are going to generate them, and that decision could invoice deciding if you are going to implement easy releases, full history, etc.
• Similarly, some modeling suggestions involve using different releases to track changes, e..g amendments. So, during the mapping you should know already if you are implementing the full change history or not, to determine how to model and track changes.
• Listing fields and data sources is one step of the mapping, but another important part is to document how to link all the different listed data sources, if possible. We should document or suggest thinking about that as part of the mapping.

@fppenna @allakulov @ndrhzn please add more learnings or insights we should document and I might missed, thanks!