#34997 - post receive spec

What does this MR do?

This removes uses of expect_any_instance_of and allow_any_instance_of in favour of the more specific allow_next_instance_of and expect_next_instance_of, adding a new helper to make this easier, since they do not share the same API.

See: #34997 (closed)

New features:

A new helper is provided: AfterNextHelpers

This allows us to reduce boilerplate by replacing

expect_next_instance_of(SomeClass) do |instance|
  expect(instance).to receive(:some_method).with(:x, :y).and_call_original
end

With:

expect_next(SomeClass).to receive(:some_method).with(:x, :y).and_call_original

This also supports allow:

allow_next(SomeClass).to receive(:some_method).and_return(double)

A specialized helper is provided for the common case of expecting services to be called:

expect_execution_of(SomeService)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done