Querying workflows by variable content

[fjtirado]

Description

Often users have to retrieve process instances using information within the process instances (aka workflow data).
At the moment it's not possible to write a graphql query to retrieve workflow instances based on the workflow variable content.
 
 
The current grapql schema is capable of handling

ProcessInstances (where:{state:{equal:COMPLETED}}) {
    variables,
    state,
    lastUpdate,
    nodes {
      name
    }
  }

but variables fileld is not filterable, so currently we cannot write

ProcessInstances (where:{variables:{workflowdata:{language:{equal:Spanish}}}}) {
    variables,
    state,
    lastUpdate,
    nodes {
      name
    }
  }

Implementation ideas

No response