feat: add EXISTS/NOT_EXISTS subquery logical where criteria expressions

[igdianov]

This PR adds support for EXISTS / NOT_EXISTS subquery logical where criteria expressions, i.e. given:

query {
  Tasks(where: {
    status: {EQ: COMPLETED}
    AND: [{
      EXISTS: {
        variables: {
          name: {EQ: "variable1"}
          value: {EQ: "data"}
        }
      }
    } {
      EXISTS: {
        variables: {
          name: {EQ: "variable2"}
          value: {EQ: true}
        }
      }
    }]
  }) {
    select {
      id
      status
      variables {
        name
        value
      }
    }
  }
}

Will return task entity if there exists both variables with name and values:

{
  "data": {
    "Tasks": {
      "select": [
        {
          "id": "1",
          "status": "COMPLETED",
          "variables": [
            {
              "name": "variable1",
              "value": "data"
            },
            {
              "name": "variable2",
              "value": true
            }
          ]
        }
      ]
    }
}

Alternative implicit AND EXISTS subquery list criteria expression:

query {
  Tasks(where: {
    status: {EQ: COMPLETED}
    EXISTS: [{
      variables: {
        name: {EQ: "variable1"}
        value: {EQ: "data"}
      }
    } {
      variables: {
        name: {EQ: "variable2"}
        value: {EQ: true}
      }
    }]
  }) {
    select {
      id
      status
      variables {
        name
        value
      }
    }
  }
}

[codecov]

Codecov Report

Merging #151 into master will increase coverage by 1.33%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #151      +/-   ##
============================================
+ Coverage     68.23%   69.56%   +1.33%     
- Complexity      440      450      +10     
============================================
  Files            33       33              
  Lines          2254     2343      +89     
  Branches        337      343       +6     
============================================
+ Hits           1538     1630      +92     
+ Misses          578      576       -2     
+ Partials        138      137       -1

Impacted Files	Coverage Δ	Complexity Δ
...a/query/schema/impl/QraphQLJpaBaseDataFetcher.java	73.98% <100%> (+2.33%)	156 <0> (+7)	⬆️
...entures/graphql/jpa/query/schema/impl/Logical.java	100% <100%> (ø)	3 <0> (ø)	⬇️
...jpa/query/schema/impl/GraphQLJpaSchemaBuilder.java	88.76% <100%> (+1.08%)	123 <3> (+3)	⬆️

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