Update integration request with missing field

[koushik-swaminathan]

The current request body in the terraform provider does not match the one given in the official documentation. This PR updates the request body to include the missing fields.
https://docs.opsgenie.com/docs/integration-api#create-api-based-integration

[arjunrajpal]

As per
https://go.dev/doc/go1.13
https://go.dev/doc/go1.14
https://go.dev/doc/go1.15
https://go.dev/doc/go1.16
Most of the changes are in the implementation of the toolchain, runtime, and libraries. We expect almost all Go programs to continue to compile and run as before.

So we shouldn't have any problems with bumping up Go

[coveralls]

coverage: 39.184%. remained the same
when pulling cb1c49e on modify-integration-request
into 07b7fdb on master.