Add missing attributes for Project Access Tokens to Audit Event API

Summary

When retrieving audit event data for project access token being created or revoked there are a few attributes missing from the response.

Merge Request !51660 (merged) that introduce Project Access Tokens into Audit Event

~bug identified in Slack

Steps to reproduce

1. Setup or access a project with at least maintainer privileges.
2. Create and revoke a project access token
3. GET a response for those Audit Events
4. Check the response for the missing attributes author_name and target_type

Example Project

https://gitlab.com/sciops/test/-/audit_events

@tancnle has access ☝

What is the current bug behavior?

Response returns missing author_name and target_type

    {
        "id": 498183325,
        "author_id": 6193108,
        "entity_id": 21575273,
        "entity_type": "Project",
        "details": {
            "target_details": "austins_test_token (read api only)",
            "action": "custom",
            "custom_message": "Revoked project access token with token_id: 3642271",
            "ip_address": "0.0.0.0",
            "entity_path": "sciops/test"
        },
        "created_at": "2021-06-11T14:11:09.656Z"
    },
    {
        "id": 498180904,
        "author_id": 6193108,
        "entity_id": 21575273,
        "entity_type": "Project",
        "details": {
            "target_details": "austins_test_token (read api only)",
            "action": "custom",
            "custom_message": "Created project access token with token_id: 3642271 with scopes: [\"read_api\"]",
            "ip_address": "0.0.0.0",
            "entity_path": "sciops/test"
        },
        "created_at": "2021-06-11T14:06:49.808Z"
    },

What is the expected correct behavior?

Response returns with author_name and target_type

    {
        "id": 498183325,
        "author_id": 6193108,
        "entity_id": 21575273,
        "entity_type": "Project",
        "details": {
            "author_name": "Austin Regnery"
            "target_type": "Project access Token"
            "target_details": "austins_test_token (read api only)",
            "action": "custom",
            "custom_message": "Revoked project access token with token_id: 3642271",
            "ip_address": "0.0.0.0",
            "entity_path": "sciops/test"
        },
        "created_at": "2021-06-11T14:11:09.656Z"
    },
    {
        "id": 498180904,
        "author_id": 6193108,
        "entity_id": 21575273,
        "entity_type": "Project",
        "details": {
            "author_name": "Austin Regnery"
            "target_type": "Project access Token"
            "target_details": "austins_test_token (read api only)",
            "action": "custom",
            "custom_message": "Created project access token with token_id: 3642271 with scopes: [\"read_api\"]",
            "ip_address": "0.0.0.0",
            "entity_path": "sciops/test"
        },
        "created_at": "2021-06-11T14:06:49.808Z"
    },

Possible fixes