Clarified intent_to_retain value when not present

[Sakurann]

resolves #669 and potentially #642 - need to discuss if we want to add additional text to clarify usage of use is not mandatory

[selfissued]

We should not be creating a default interpretation of not specifying this parameter in a way that requires changes to existing wallets.

[jogu]

resolves #669 and potentially #642 -

I don't think this touches #642.

[jogu]

I can't find any place where we actually reached a conclusion on what we should do.

#669 (comment) says:

explicitly stating that intent_to_retain being optional means that the verifier is not specifying if it will retain or not, which is arguably what the current spec says.

[brentzundel]

discussed in call today. Some suggested changes to the text were made.

[brentzundel]

Seemed to be consensus that if the verifier is not expressing anything, the wallet should indicate that the verifier hasn't expressed anything.

[c2bo]

Suggested change

	: OPTIONAL. A boolean that is equivalent to `IntentToRetain` variable defined in Section 8.3.2.1.2.1 of [@ISO.18013-5]. If not specified, the Wallet uses the value `false`.
	: OPTIONAL. A boolean that is equivalent to `IntentToRetain` variable defined in Section 8.3.2.1.2.1 of [@ISO.18013-5]. If absent, the Verifier makes no statement on `IntentToRetain`.

[c2bo]

Suggested change

	: OPTIONAL. A boolean that is equivalent to `IntentToRetain` variable defined in Section 8.3.2.1.2.1 of [@ISO.18013-5]. If not specified, the Wallet uses the value `false`.
	: OPTIONAL. A boolean that is equivalent to `IntentToRetain` variable defined in Section 8.3.2.1.2.1 of [@ISO.18013-5]. If absent, the Verifier makes no statement on `IntentToRetain`.