[management] Better select plan based on subscription

[jhaeyaert]

Since #6528, selection of the subscription during the security chain execution is not perfect.

When dealing with multiple plans based on the same security type, the policy is applied prior to retrieve the associated subscription that needs to checked (same security type -> JWT and Oauth2 are both based on Authorization bearer token).

This is not optimal because, in some circumstances, it can select a subscription that is not linked to the plan that has been executed.
We must rethink the way plans are selected and executed by reordering the different steps:

1. extract the information which identify the caller (clientId, apikey, ...)
2. identify the subscription
3. identify the plan associated to the subscription
4. execute the plan

[marcambier]

@RubenMMSantos @LiliaEn, a simple test case for this ticket :

• api1 with 2 JWT plans : JWT1 and JWT2

• app1 is subscribed to JWT1

• app2 is subscribed to JWT2

• call the API using app1 subscription : it works

• call the API using app2 subscription : it works

• add a selection rule on JWT1

• call the API using app1 subscription, matching selection rule : it works

• call the API using app1 subscription, not matching selection rule : unauthorized

• remove selection rule on JWT1

• add a selection rule on JWT2

• call the API using app2 subscription, matching selection rule : it works

• call the API using app2 subscription, not matching selection rule : unauthorized

• remove selection rule on JWT2

Additionnally, we have to check non-regression of all that is about JWT / Oauth2 plans and their selection rules.

[LiliaEn]

The following scenarios were covered:

• JWT+JWT plans on the same API
  The correct plan is selected when a using a selection rule.
  When there is no selection rule applied, depending on the token used, the appropriate plan gets executed.
  When the selection rule is not matched, the appropriate error is displayed
• JWT+oAUTH2 plans on the same API
  The correct plan is selected when a using a selection rule.
  When there is no selection rule applied, depending on the token used, the appropriate plan gets executed.
  When the selection rule is not matched, the appropriate error is displayed
• JWT+oAUTH2+ API Key
  The correct plan is selected when a using a selection rule.
  When there is no selection rule applied, depending on the token/ api key used, the appropriate plan gets executed.
  When the selection rule is not matched, the appropriate error is displayed

[RubenMMSantos]

Oauth2_plan+ Oauth2_plan scenario not working as expected, 1st plan is always overwriting the 2nd one in terms of behaviour (in terms of policies and selection_rules).
Confirmed with @marcambier that this will be fixed on Jupiter via ticket #7991 but cannot be fixed on existing V3 gateway so moving the ticket to done so it does not block the other fixes in the ticket