OpenMLS Updates

[zombieobject]

While I was able to merge and resolve the conflicts in the upstream merge, I do get the following error output during cargo build. It's most likely that I made some flawed choices during conflict resolution.

warning: unused variable: `group_keypairs`
   --> openmls/src/group/core_group/new_from_welcome.rs:177:13
    |
177 |         let group_keypairs = if let Some(path_secret) = path_secret_option {
    |             ^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_group_keypairs`
    |
    = note: `#[warn(unused_variables)]` on by default

error[E0382]: use of moved value
   --> openmls/src/group/core_group/new_from_welcome.rs:246:41
    |
127 |         let path_secret_option = group_secrets.path_secret;
    |                                  ------------------------- value moved here
...
246 |         let path_keypairs = if let Some(path_secret) = group_secrets.path_secret {
    |                                         ^^^^^^^^^^^ value used here after move
    |
    = note: move occurs because `group_secrets.path_secret` has type `std::option::Option<messages::PathSecret>`, which does not implement the `Copy` trait

error[E0382]: use of moved value: `leaf_keypair`
   --> openmls/src/group/core_group/new_from_welcome.rs:274:13
    |
32  |         let leaf_keypair = EncryptionKeyPair::read_from_key_store(
    |             ------------ move occurs because `leaf_keypair` has type `encryption_keys::EncryptionKeyPair`, which does not implement the `Copy` trait
...
192 |             vec![leaf_keypair]
    |                  ------------ value moved here
...
197 |             vec![leaf_keypair]
    |                  ------------ value moved here
...
274 |             leaf_keypair,
    |             ^^^^^^^^^^^^ value used here after move
    |
help: consider cloning the value if the performance cost is acceptable
    |
197 |             vec![leaf_keypair.clone()]
    |                              ++++++++
help: consider cloning the value if the performance cost is acceptable
    |
192 |             vec![leaf_keypair.clone()]
    |                              ++++++++

For more information about this error, try `rustc --explain E0382`.
warning: `openmls` (lib) generated 1 warning
error: could not compile `openmls` (lib) due to 2 previous errors; 1 warning emitted

[github-actions]

This PR is so big! Please, split it 😊

[zombieobject]

Getting shamed by a GitHub action for an upstream merge is an achievement unlocked. Where's my badge? 🤣