Allow space to complete an email address in recipient fields

Checklist

• I have used the search function to see if someone else has already submitted the same feature request.
• I will describe the problem with as much detail as possible.
• This issue only contains a request for one single feature, not multiple (related) features.

App version

6.000

Problem you are trying to solve

User wants to send a message to two recipients and performs the following steps:

1. Open screen to compose a new message (To field has the focus)
2. Enter text user1@domain.example user2@domain.example
3. Change focus to another field

K-9 Mail does not recognize two addresses separated by a space. It will try to parse it as one address and display an "Error parsing address!" error.

Suggested solution

Support "completing" an email address using a space character.

This is a bit tricky because a space might also be part of the display name, e.g. Firstname Lastname <user@domain.example> second.user@domain.example.

Note

Fixing this probably involves writing a custom email address parser and changing the way the TokenAutoComplete library works (or replacing it entirely). It's not something someone new to the project should attempt.

No source files or tests are named. Start by investigating the recipient fields and the TokenAutoComplete library, then define how space completion should distinguish multiple addresses from spaces in display names; done means both cases parse correctly.