WordPress REST API Basic Authentication - php

Question

I am working on a project that requires some integration between different WordPress instances and I am in the process of creating a WordPress plugin that will provide that functionality through the REST API.
I have enabled the WP-API plugin and the Basic Authentication plugin and am able to make requests that do not require authentication but when I make a request that does require authentication, such as adding a new page, I am met with 401 - Sorry, you are not allowed to create new posts.
I realize basic authentication is not suitable for production needs but would like to get it working properly for development and have been spinning my wheels on this seemingly small problem. I am perfectly able to make these requests using Postman, so there is something wrong with my implementation. Here is the code in question:
function add_new_page($post) {
// Credentials for basic authentication.
$username = 'user';
$password = 'password';
// Request headers.
$headers = array(
'Authorization' => 'Basic ' . base64_encode( $username . ':' . $password ),
'Content-Type' => 'application/json'
);
// Request URL.
$url = "http://localhost/wp-json/wp/v2/pages";
// Request body.
$body = array(
'slug' => $post->post_name,
'status' => $post->post_status,
'type' => $post->post_type,
'title' => $post->post_title,
'content' => $post->post_content,
'excerpt' => $post->post_excerpt,
);
$body_json = json_encode($body);
// Request arguments.
$args = array(
'method' => 'POST',
'blocking' => true,
'headers' => $headers,
'cookies' => array(),
'body' => $body_json,
);
// Fire request.
$response = wp_remote_request($url, $args);
// Handle response.
if (is_wp_error($response)) {
$error_message = $response->get_error_message();
echo "Something went wrong: $error_message";
} else {
$response_body = json_decode(wp_remote_retrieve_body($response));
// Display response body.
echo '<pre>';
print_r($response_body);
echo '</pre>';
}
// Exit so we can read the response.
exit();
}
I would be really appreciative of any insights somebody out there could provide.