adding credential issuer logo parameter in the issuer metadata (#170)

7 approvals. open for more than a week. no objections to merge during the last WG call.

* adding credential issuer logo uri based on PR #141

* Apply editorial suggestions from code review

* make uri required

* typo

Co-authored-by: Joseph Heenan <joseph@heenan.me.uk>

* change logo uri for each credential to be required too

* Apply suggestions from Mike's code review

* Apply suggestions from Mike's code review

Co-authored-by: Michael B. Jones <michael_b_jones@hotmail.com>

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Co-authored-by: Kristina <=>
Co-authored-by: Joseph Heenan <joseph@heenan.me.uk>
Co-authored-by: Michael B. Jones <michael_b_jones@hotmail.com>

openid-4-verifiable-credential-issuance-1_0.md

@@ -1343,6 +1343,9 @@ This specification defines the following Credential Issuer Metadata:
 * `display`: OPTIONAL. Array of objects, where each object contains display properties of a Credential Issuer for a certain language. Below is a non-exhaustive list of valid parameters that MAY be included:
   * `name`: OPTIONAL. String value of a display name for the Credential Issuer.
   * `locale`: OPTIONAL. String value that identifies the language of this object represented as a language tag taken from values defined in BCP47 [@!RFC5646]. There MUST be only one object for each language identifier.
+  * `logo`: OPTIONAL. Object with information about the logo of the Credential Issuer. Below is a non-exhaustive list of parameters that MAY be included:
+    * `uri`: REQUIRED. String value that contains a URI where the Wallet can obtain the logo of the Credential Issuer. The Wallet needs to determine the scheme, since the URI value could use the `https:` scheme, the `data:` scheme, etc.
+    * `alt_text`: OPTIONAL. String value of the alternative text for the logo image.
 * `credential_configurations_supported`: REQUIRED. Object that describes specifics of the Credential that the Credential Issuer supports issuance of. This object contains a list of name/value pairs, where each name is a unique identifier of the supported Credential being described. This identifier is used in the Credential Offer as defined in (#credential_offer_parameters) to communicate to the Wallet which Credential is being offered. The value is an object that contains metadata about specific Credential and contains the following parameters defined by this specification:
   * `format`: REQUIRED. A JSON string identifying the format of this Credential, i.e., `jwt_vc_json` or `ldp_vc`. Depending on the format value, the object contains further elements defining the type and (optionally) particular claims the Credential MAY contain and information about how to display the Credential. (#format_profiles) defines Credential Format Profiles introduced by this specification.
   * `scope`: OPTIONAL. A JSON string identifying the scope value that this Credential Issuer supports for this particular Credential. The value can be the same across multiple `credential_configurations_supported` objects. The Authorization Server MUST be able to uniquely identify the Credential Issuer based on the scope value. The Wallet can use this value in the Authorization Request as defined in (#credential-request-using-type-specific-scope). Scope values in this Credential Issuer metadata MAY duplicate those in the `scopes_supported` parameter of the Authorization Server.
@@ -1353,7 +1356,7 @@ This specification defines the following Credential Issuer Metadata:
       * `name`: REQUIRED. String value of a display name for the Credential.
       * `locale`: OPTIONAL. String value that identifies the language of this object represented as a language tag taken from values defined in BCP47 [@!RFC5646]. Multiple `display` objects MAY be included for separate languages. There MUST be only one object for each language identifier.
       * `logo`: OPTIONAL. Object with information about the logo of the Credential with a following non-exhaustive list of parameters that MAY be included:
-          * `uri`: OPTIONAL. String value that contains a URI where the Wallet can obtain a logo of the Credential from the Credential Issuer. Wallet needs to determine the scheme, since the URI value could use `https:` scheme, `data:` scheme, etc.
+          * `uri`: REQUIRED. String value that contains a URI where the Wallet can obtain the logo of the Credential from the Credential Issuer. The Wallet needs to determine the scheme, since the URI value could use the `https:` scheme, the `data:` scheme, etc.
           * `alt_text`: OPTIONAL. String value of an alternative text of a logo image.
       * `description`: OPTIONAL. String value of a description of the Credential.
       * `background_color`: OPTIONAL. String value of a background color of the Credential represented as numerical color values defined in CSS Color Module Level 37 [@!CSS-Color].