(no ticket): [revise] query param include should accept comma separated list of values

[matthewvolk]

What changed?

For context, this PR originated from: matthewvolk/bigrequest#84 as a solution for inconsistent Typescript type definitions being generated from our OpenAPI spec files. I haven't checked if these changes introduce any unintended side effects to other ways our spec files are consumed!

• Refactors the schema definition of the include query parameter across various API endpoints to indicate that include accepts a comma-separated list of enum values, rather than one-of an enum value.
• A schema with type: string and enum: [value1,value2] resolves to: ?include=[value1|value2] (either value1 or value2) (source: swagger.io)
• If we instead describe the schema as a type: array, where the items in the array are of type: string and can be one or more of items.enum: [value1,value2] the schema now resolves to: ?include=[value1[,value2]
• explode: false is also added to indicate that query parameter values can be expressed in the format: /users?id=3,4,5 as opposed to /users?id=3&id=4&id=5 (source: swagger.io))

Anything else?

There are a number of locations in other files that we may want to apply these changes to, but I haven't confirmed that each location accepts a comma separated list of strings. Here is a list: https://github.com/search?q=repo%3Abigcommerce%2Fapi-specs%20%22-%20name%3A%20include%22&type=code

[matthewvolk]

fixes matthewvolk/bigrequest#84

[slsriehl]

thank @matthewvolk !