Changelog: other
EE: true

- `lib/**`

With this, we'll emit 2 new counters from web processes that can be
used to monitor apdex.

The `gitlab_sli:rails_request_apdex:total` counter is incremented for
every successful (not a 500) that is not to a health endpoint.

The `gitlab_sli:rails_request_apdex:success_total` is incremented when
the request took less than 1 second. We intend to customize this value
per endpoint in the future.

Both these counters are labelled with `feature_category` and
`endpoint_id` from the context.

The metrics would also be initialized on the first scrape. This means
that a 0 would be available for every set of labels, avoiding bugs in
calculations with these metrics.

To get to all of the `feature_category`s and `endpoint_id`s for the
initialization, we had to move some code that iterates all endpoints
that was only used in tests to the application.

We know this would initialize about 2 * 2500 metrics per pod
running a web server. So we'd like to roll this out in a controlled
fashion, to make sure this doesn't impact our monitoring. Which is why
this is feature flagged.

This also limits the initialization of these metrics to just
web-processes. So they don't get generated for consoles or runner
processes.

This also includes a developer-api to define SLIs and encourages
initializing them with the known label sets.

This adds the request method to the endpoint_id and caller_id
metadata for Grape requests. This allows us to differentiate routes if
they have the same path but different methods.

This brings back many of the changes in
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/27276. This was
reverted due to some failures in the QA tests with nil parameters.

Grape v1.3.3 brings in Ruby 2.7 support and a number of fixes:
https://github.com/ruby-grape/grape/blob/master/CHANGELOG.md

1. Move all inherited `Grape::API` -> `Grape::API::Instance`
2. Remove use of Virtus since this has been removed from Grape.
3. Extract `Rack::Response` from API error
4. Grape v1.2.3 pulled in a fix used in `SafeFile`:
https://github.com/ruby-grape/grape/pull/1844, so we no longer need
to maintain our custom type.
5. Adapt `WorkhorseFile` with the latest changes to make custom types
work with Grape and dry-types.
6. Ensure `Array[String]` is coerced properly.

The change from Virtus to dry-types now requires all strings to be
coerced to arrays. Before this was done within Virtus.

7. Coerce `Array[Integer]` types to arrays of integers

8. Use a new helper, `coerce_nil_params_to_array!`, that coerces nil
Array inputs to empty arrays to preserve previous behavior.

If you have a parameter of type `Array[String]`, for example, Grape used
to coerce a provided `nil` value to `[]`. Grape no longer does this for
us, so we need a helper method that will automatically do this if the
parameter is present.

This merge request also introduces two Rubocop rules for Grape v1.3:

1. `Grape::API::Instance` instead of `Grape::API` is required, unless we
solve https://gitlab.com/gitlab-org/gitlab/-/issues/215230.

2. Grape parameters defined with `Array` types (e.g. `Array[String]`,
`Array[Integer]`) must have a `coerce_with` block or they will fail to
parse properly. See
https://github.com/ruby-grape/grape/blob/master/UPGRADING.md for more
details.

Extend issues API by
* Accepting epic_id parameter when creating a new issue. (POST)
* Accepting epic_id parameter when updating an existing issue. (PUT)

Partially addresses #47424.

Had to make changes to spec files because
stubbing methods on frozen objects is a mess
in RSpec and leads to failures:

https://github.com/rspec/rspec-mocks/issues/1190

see https://gitlab.com/gitlab-org/gitlab-ce/issues/42025

See https://gitlab.com/gitlab-org/gitlab-ce/issues/42025