"extras" must be resolved

[stellasia]

Description

Small bug fix, where parameter under the 'extras' key were not resolved. Ie this PR allows to write config files like:

{
    "extras": {
        "openai_api_key": {
            "resolver_": "ENV",
            "key_": "MY_OPENAI_KEY"
        }
    },
    "llm_config": {
        "class_": "OpenAILLM",
        "params_": {
            "api_key": {
                "resolver_": "CONFIG_KEY",
                "key_": "extras.openai_api_key"
            }
        }
    },
    "embedder_config": {
        "class_": "OpenAIEmbeddings",
        "params_": {
            "api_key": {
                "resolver_": "CONFIG_KEY",
                "key_": "extras.openai_api_key"
            }
        }
    }
}

Note: this was the intention with the addition of the extras field in config file, but using the wrong type is preventing it to be resolved as intended.

Type of Change

• New feature
• Bug fix
• Breaking change
• Documentation update
• Project configuration change

Complexity

Complexity: Low

How Has This Been Tested?

• Unit tests
• E2E tests
• Manual tests

Checklist

The following requirements should have been met (depending on the changes in the branch):

• Documentation has been updated
• Unit tests have been updated
• E2E tests have been updated
• Examples have been updated
• New files have copyright header
• CLA (https://neo4j.com/developer/cla/) has been signed
• CHANGELOG.md updated if appropriate