[Bug] Support more behavior for mailto: links

[nmanngit]

Describe the bug
Other mail clients, including Windows Mail, support more behavior for mailto: links, such as setting multiple recipients and including recipients in the ?to attribute. Setting multiple recipients crashes the app, using ?to won't fill out the recipients.

Expected behavior
If I understand it correctly, in terms of RFC 6068 the following should be possible:

• mailto:[email protected]
• mailto:?to=[email protected]
• mailto:[email protected],[email protected]
• mailto:?to=[email protected],[email protected]

Additional context
Old Outlook only supports ; as a separator for some reason, new Outlook and Windows Mail support both , and ; while Apple Mail seems to only support , as in the spec.

In addition, some clients support adding the recipients name to the mail address. This can somethimes be helpful. Even though Apple Mail and Outlook new seem to support it, it doesn't seem to be in the spec:

❓ mailto:Test<[email protected]>

[bkaankose]

There is one problem with improving this one: dotnet/runtime#30300

WinRT delivers the protocol activation link to Wino as Uri. Since the Uri will be invalid due to the issue described above, Wino can only support as many as it can extract. We can't create our own parser around the plain protocol link since we don't have access to it.

@Tiktack's PR #310 improves the existing mailto links, but can't resolve all unfortunately.

[Tiktack]

Supported use cases can be seen below ( Use cases with "Uri issue" is not working due to runtime issue mentioned by @bkaankose):

[bkaankose]

v1.9.0 that addressed this issue is released to the Store. Please re-test and re-open if you can still reproduce it.

Closing as fixed.