CDRIVER-4689 Implement OIDC machine callback

[kevinAlbs]

Summary

Implement Machine Authentication Flow for OIDC auth. This enables using the MONGODB-OIDC auth mechanism with a user-supplied callback giving the access token. Integrating other identity providers is planned in future work: Azure (CDRIVER-4548) and GCP (CDRIVER-4611).

• Add OIDC callback setters: mongoc_client_set_oidc_callback and mongoc_client_pool_set_oidc_callback.
• Add binary operation to the BSON DSL to help construct the OIDC commands.

Tested with https://spruce.mongodb.com/version/68e90bef5727ed0007c8e376

Background & Motivation

mongoc_cluster_run_command_monitored checks for a ReauthenticationRequired error from the server and retries once. Ths same change is not made in mongoc_cluster_run_command_parts or mongoc_cluster_run_command_private (used for auth commands, and not expected to need retry).

mongoc_client(_pool)_set_oidc_callback returns a bool and logs on error for consistency with other recently added setters like mongoc_client(_pool)_set_structured_log_opts.

Testing

Evergreen tasks are added following Scripts for OIDC testing > Evergreen Testing.

Tests can be run locally by starting the OIDC-enabled server:

export AWS_PROFILE
$DRIVERS_TOOLS/.evergreen/auth_oidc/start_local_server.sh

Then running:

export MONGOC_TEST_USER="bob"
export MONGOC_TEST_PASSWORD="pwd123"
export MONGOC_TEST_OIDC="ON"
./cmake-build/src/libmongoc/test-libmongoc --no-fork -d \
    --match "/auth/unified/*" \
    --match "/oidc/*"

[connorsmacd]

(Nitpick) I don't think this comment is adding any useful context.

[kevinAlbs]

Agreed. Removed.

[connorsmacd]

Looks like you could flatten this a bit, e.g.:

if (run_command_monitored(cluster, cmd, reply, error)) {
    return true;
}

// rest of the function body

[kevinAlbs]

Nice. Updated.

[connorsmacd]

Superfluous compound statement since the braces after the if already form a compound statement.

[connorsmacd]

LGTM!