Stabilize order of parameter objects and preserve objects with newer example - #59

This is a spin-out from #57
After this PR, parameters array preserves the occurrence with newer value in example

Current implementation

It keeps the first occurrence of duplicated items with same name & in.
If user update an existing parameter in their rspec, a new parameter object with newer value in example fieldis added to parameters` array ... but is removed soon because it is not the first occurrence.
In other words, the occurrence with oldest example is kept forever.

Problems

"Preserving first occurrence" will cause a problem for some cases.

1. User changed the value format.

Let's say user changed the format of id from numeric (123) to ulid (01ARZ3NDEKTSV4RRFFQ69G5FAV).

• Base spec, [{ name: "id", in: "path", example: "123" }]
• After merge, [{ name: "id", in: "path", example: "123" }, { name: "id", in: "path", example:"01ARZ3NDEKTSV4RRFFQ69G5FAV" }]
• After deduplication, [{ name: "id", in: "path", example: "123" }]

😭 The preserved 123 is wrong about format.

2. rspec-openapi support another field of parameter object

Let's say rspec-openapi added description field in parameter object somehow.

• Base spec, [{ name: "id", in: "path", example: "123" }]
• After merge, [{ name: "id", in: "path", example: "123" }, { name: "id", in: "path", example:"123", description:"blah blah" }]
• After deduplication, [{ name: "id", in: "path", example: "123" }]

😭 description is not added.

Solution

1. Keep a last occurrence

Unfortunately, it brings unstable order.
Let's say we invokes /foo/123 and /foo/456 in rspec.

• 1st run
  • Base spec, [{ name: "id", in: "path", example: "123" }]
  • After merge, [{ name: "id", in: "path", example: "123" }, { name: "id", in: "path", example:"456" }]
  • After deduplication, [{ name: "id", in: "path", example: "456" }]
• 2nd run: (just rerun)
  • Base spec, [{ name: "id", in: "path", example: "456" }]
  • After merge, [{ name: "id", in: "path", example: "456" }, { name: "id", in: "path", example: "123" } ]
  • After cleanup, [{ name: "id", in: "path", example: "123" }]

😭 123 and 456 is oscillating for each run.

2. Introduces a timestamp marker to be used as sort key

I think it is better to introduce __marker: Timestamp field to parameters.
Then, merger sorts the parameters and preserves the duplicates with largest __marker, so the older occurrencenes will be removed.

This PR also sorts parameters by in and name before __marker, because sort_by is not "stable sort"