[Openid-specs-ab] Issue #1819: [Federation] Policy language: New equals | set_equals value check (openid/connect)

[Vladimir Dzhuvinov]

New issue 1819: [Federation] Policy language: New equals | set_equals value check
https://bitbucket.org/openid/connect/issues/1819/federation-policy-language-new-equals

Vladimir Dzhuvinov:

Purpose: To define equality checks for metadata parameters.

Example use case: Enforcing `client_registration_types` be equal to `["automatic"]`, “explicit” must not be supported.

Possible variants:

* `equals` – applies to JSON entities that are strings, numbers, true|false, objects and arrays \(arrays should be treated as sets, because the item order does not matter in present known metadata cases\).  
* `set_equals` – applies strictly to JSON entities that are arrays

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Example, `equals` variant:

```json
"client_registration_types" : {
    "equals": ["automatic"]
},
"application_type": {
    "equals": "web"
}
```

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Example, `set_equals` variant:

```json
"client_registration_types" : {
    "set_equals": ["automatic"]
}
```

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