[pgadmin4] Explain plans

Move the SQL to generate explain plans to backend
For this approach we would create a new endpoint to generate an explain plan and when we click the explain plan buttons instead of doing a new SQL query we would call the new endpoint and wait for the explain plan to be generated

• Pros:
  • All SQL related code is in the backend
  • Extract more code from SQLEditor into smaller and more testable/maintainable modules
• Cons:
  • Major Revamp of SQLEditor
  • If explain plan takes to long to generate we will be waiting for it in the foreground instead of polling

Add parameters while executing SQL
If we add parameters in the SQL query request we send to the backend, informing the backend that the SQL query is a Explain Plan to be executed(The response can have a flag saying that this is an explain plan, instead of assuming from the return values that it was an explain plan)

• Pros:
  • All SQL related code is in the backend
  • Leverage the current polling system
• Cons:
  • Add more logic to an already complex SQLEditor

Disable Explain plan buttons
Disable/Enable the Explain plan buttons depending on the type of database, this would also include the tab in the bottom of the SQLEditor

• Pros:
  • Simpler solution
• Cons:
  • Not really a good implementation, because all databases support explain plans
  • There will still be SQL in both frontend and backend
  • Looks more like a temporary fix instead of a solution