feat: filter process instances by multiple variables and return bpmn groups, documentation, and extensionProperties in process details

[HMubaireek]

Description

This PR adds the following features:

• Allows filtering process instances by process variables:

{
  process(key: 2251799813712348){
    key
    processInstances(variablesFilter: {
      variables : [
      {
        name: "userEmail", 
        value:"myemail@gmail.com",
        comparisonOperation: EQUALS
      },
      {
        name: "processType", 
        value:"My Process Type",
        comparisonOperation: CONTAINS
      }          
      ],
      filterOperation: OR
    }
    ) {
      totalCount
      nodes {
        key
        variables(globalOnly: true){
           name
          value
        }
      }
    }
  }
}

• Return documentation and extensionProperties along with process elements. In addition, allow returning bpmn:group elements since before it was only returning elements of type FlowElement

{
  process(key: 2251799813712348){
    key
    elements {
      elementId
      bpmnElementType
      extensionProperties {
        name
        value
      }
      documentation
    }
  }
}

Related issues

For filtering by variables:
closes # #16

For returning documentation, group, and extensionProperties:
closes # #356

[saig0]

@HMubaireek thank you for your contribution. 🎉 I'll have a look at the changes next week. 👀

[saig0]

@HMubaireek I did a quick review of your changes. Looks good in general. 🚀

I have concerns about the performance of the variables filtering and a few minor suggestions.

To speed up the review, please split up the changes into two PRs for the new BPMN element properties and the variables filtering. And, add some test cases to verify the behavior. 🍪

---

I'm sorry for the delay. Looking forward to the new features. ✨