Implement explorations.run RPC endpoint

[Anish9901]

Fixes #3715

Important

Some notable changes to the request object.

• base_table -> base_table_oid
• id -> attnum
• jp_path -> join_path
• join_path should be an ordered list of in the form [[left_table_oid, attnum], [right_table_oid, attnum]]

Request

{
  "base_table_oid": 2254329,
  "initial_columns": [
    {"attnum": 2, "alias": "Checkouts_Item"},
    {
      "attnum": 5,
      "alias": "Books_Page Count",
      "join_path": [
        [ [2254329, 2], [2254334, 1] ],
        [ [2254334, 5], [2254321, 1] ]
      ]
    }
  ],
  "transformations": [],
  "display_names": {
    "Checkouts_Item"  : "Checkouts_Item"  ,
    "Books_Page Count": "Books_Page Count"
  }
}

Response

{
  "query": {
    "base_table_oid": 2254329,
    "initial_columns": [
      {"attnum": 2, "alias": "Checkouts_Item"},
      {
        "attnum": 5,
        "alias": "Books_Page Count",
        "join_path": [
          [ [2254329, 2], [2254334, 1] ],
          [ [2254334, 5], [2254321, 1] ]
        ]
      }
    ],
    "transformations": [],
    "display_names": {
      "Checkouts_Item"  : "Checkouts_Item"  ,
      "Books_Page Count": "Books_Page Count"
    }
  },
  "records": {
    "count": 14929,
    "results": [
      {"Checkouts_Item":  1, "Books_Page Count": 368},
      {"Checkouts_Item":  1, "Books_Page Count": 368},
      {"Checkouts_Item":  1, "Books_Page Count": 368},
      {"Checkouts_Item":  1, "Books_Page Count": 368},
      {"Checkouts_Item":  1, "Books_Page Count": 368},
      {"Checkouts_Item":  1, "Books_Page Count": 368},
      {"Checkouts_Item":  1, "Books_Page Count": 368},
      [...more]
    ]
  },
  "output_columns": ["Checkouts_Item", "Books_Page Count"],
  "column_metadata": {
    "Checkouts_Item": {
      "alias": "Checkouts_Item",
      "display_name": "Checkouts_Item",
      "type": "integer",
      "type_options": null,
      "display_options": null,
      "is_initial_column": true,
      "input_column_name": "Item",
      "input_table_name": "Checkouts",
      "input_table_id": 2254329,
      "input_alias": null
    },
    "Books_Page Count": {
      "alias": "Books_Page Count",
      "display_name": "Books_Page Count",
      "type": "integer",
      "type_options": null,
      "display_options": null,
      "is_initial_column": true,
      "input_column_name": "Page Count",
      "input_table_name": "Books",
      "input_table_id": 2254321,
      "input_alias": null
    }
  },
  "parameters": {}
}

Checklist

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the develop branch of the repository
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no
  visible errors.

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[mathemancer]

Overall, things look good and I like the methodology. I did request a change which should be pretty simple for the API-facing function signature. The reason is that I'd like to align this with the records.list call style when it's easy, and that seems like low-hanging fruit.

[Anish9901]

I do think that we should make the documentation for the transformations better but I don't have enough context on how its used by the frontend.

[mathemancer]

This looks good to me.