3.2: schema test coverage

[ralfhandl]

• fixes a bug in the Link Object schema
  • 3.1 3.2 schemas: Link Object schema has body property instead of server #4463
• increases schema coverage to 100%
  • files named x-object-example(s).yaml contain examples copied from the spec and completed to become valid OADs
  • file path_item_servers_parameters.yaml contains remaining cases not covered by spec examples

Tick one of the following options:

• schema changes are included in this pull request
• schema changes are needed for this pull request but not done yet
• no schema changes are needed for this pull request

[miqui]

@ralfhandl looks good.