Flatten nested objects with lodash

I'm banging my head against a well trying to do the following with lodash. I have an array of objects with more nested objects, which looks like this:

[{
    id: 123,
    name: 'John',
    summary1: {
        count: 3,
        sum: 10,
    },
    summary2: {
        count: 10,
        sum: 20
    },
},
...
]

I want to convert each element of this array into something like this:

[{
    id: 123,
    name: 'John',
    summary1_count: 3,
    summary1_sum: 10
    summary2_count: 10,
    summary2_sum: 20,
},
...
]

SO basically I want to "flatten" each element of the array, in a way such that object keys are determined based on the main and subkeys. How can I accomplish this using lodash or plain JS?

You can assume there's just 1 level of nesting like in the example.