feat: extend join tables config for types

[Zerogiven]

This pull request would give us more flexibility with JoinTables.

After it the following values are allowed:

JoinTables: ['SiteTree_Live']

JoinTables: ['SiteTree_Live.ID']

JoinTables:
  - "SiteTree_Live.ID": "Page.ID"

# Most advanced config. Set join table and on tables optional with columns
JoinTables:
  - "SiteTree_Live":
    - "SiteTree_Live.ID": "Page.ID"

All of them will produce the same output

LEFT JOIN SiteTree_Live ON SiteTree_Live.ID = Page.ID