Export & Import - Combined Report, Dashboard Entities

2nd Iteration of Export/Import feature:

• Export and Import Combined Repots
• Export and Import Dashboards
• Document import/export feature on https://docs.camunda.org/optimize/latest/ 
• Validation:
  • Same requirements as the import of single reports, same error responses
  • If multiple errors occur, they should be collected so they can be communicated in the UI as a list (use exception bodies to communicate when multiple entities have the same issues, e.g. if multiple definitions don't exist)
• Limitations:
  • Potential duplicates:
    when importing two separate combined report or dashboard files that both rely on the same single reports, these single reports will be imported again unless we implement some sort of check for potential existing duplicates
  • Only superusers will be allowed to import/export

Note for exception handling:

For this first iteration, we will gather all exceptions of one type and throw the one with the highest "priority", eg. 1) index mismatch 2) missing definition, 3) missing definition authorization. Future iterations will implement the merging of these exceptions to display a list of different import errors. 

API docs on Confluence:
https://confluence.camunda.com/display/CO/Import 
ttps://confluence.camunda.com/display/CO/Export 

Functionality not covered by this iteration (to be addressed in future iterations):

• Enable non-superusers to import/export (OPT-4768)
• Merge import exceptions to return more information about why import attempts of multiple entities failed, eg throw one "importException" that may include information on index version mismatches as well as forbidden and missing definitions
• Handle potential existing duplicates during import (eg importing a Dashboard that references a single report that already exists in the target Optimize. Ideally, the import can detect this and avoid importing the same report again)
• Import and export event based process reports (OPT-4769)
• Import and export collections (OPT-4686)
• Import and export multiple entities at ones (eg a list of collections)
  • Also implement a special import not found exception that includes a list of all entities that could not be found

What is the desired functionality that you are missing?

I can export dashboards and combined reports, so that I can import my dashboard or combined report into an Optimize instance when needed (e.g. export from development / staging environment and import into production. 

Which problem are you going to solve with this functionality?

Dashboards and Combined Reports including reports are often prepared in staging environment and once the process moves into production or dashboards have been approved dashboards and all including reports have to be recreated in the production environment. this is very time-consuming for end users.

Context

This is the second iteration of OPT-2252 which did the same for Single Process and Decision Reports.