util.roles: Add some more missing test cases Found via mutation testing.

util.promise: Fix field name in failing test (introduced in 2639e0e1c378)

util.promise: Add some missing test cases (found through mutation testing)

util.promise: Remove line that was supposed to be removed in eb9814372c54

util.promise: Remove some redundant checks, add tests confirming redundancy This lines don't appear to do anything useful, and all tests pass when they are removed. Discovered via mutation testing. I added extra tests to exercise this code, because I wasn't certain that there were no side-effects caused by removal. Everything appears to be fine, thanks to the "pending" check at the start of promise_settle().

util.roles: Add a :policies() method to iterate through available policies We don't expose the policies directly, to force people to go through :may(). However, there are times when we really just need to know what policies a role has inside it (e.g. for reporting or debugging purposes).

util.roles: Add tests

util.roles: Return nil if the role has no explicit policy (fixes inheritance) Previously, if the first inherited role had no opinion, it returned false and prevented further consultation of other inherited roles. This bug was found thanks to the implementation of missing test cases identified through mutation testing.

mod_smacks: Change boolean attribute from '1' to 'true' for compatibility Conversations 2.10.10 and earlier expect this to be literally 'true' and don't recognise '1'. This leads to it not attempting resumption with Prosody at all since this change was introduced in 36ba170c4fd0. Thanks to Zash for noticing, debugging and diagnosing this issue. This issue is fixed in Conversations commit 052c58f3 (unreleased at the time of writing).

util.iterators: join: Work even with only a single iterator in the chain