Improve summaries and descriptions for each endpoint

[bcbogdan]

Summary
The following PR improves the explanations for each endpoint in order to make the spec easier to understand for the end user.
The following changes have been added:

• Tenant ID parameter format was changed from <tenantId>, to {tenantId}, in description and all URL paths. Same for appId
  This was done to have consistency in how we present path parameters in our documentation.
• Summary fields have been added on all the endpoints
• Each. response schema now has a title and a description
• The apikey header is now included in the security configuration. This is required so that the API docs properly display the authentication requirements for each request.