Add GRAPHQL option to ScanMethodTypeEnum

What does this MR do and why?

This Merge Request adds the GRAPHQL option to ScanMethodTypeEnum.

This change is necessary to allow the creation of dast site profiles with GraphQL scan method as described in #378692 (closed).

#378692 (comment 1184898789)

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How to set up and validate locally

1. Go to /-/graphql-explorer

2. Create a query like

mutation dastSiteProfileCreate($input: DastSiteProfileCreateInput!) {
  dastSiteProfileCreate(input: $input) {
    errors
    dastSiteProfile {
      id
    }
  }
}

{
  "input": {
    "fullPath": "root/apiscantest",
    "profileName": "Test GraphQL",
    "scanMethod": "GRAPHQL",
    "targetType": "API",
    "targetUrl": "http://localhost"
  }
}

3. Check the result

{
  "data": {
    "dastSiteProfileCreate": {
      "errors": [],
      "dastSiteProfile": {
        "id": "gid://gitlab/DastSiteProfile/15"
      }
    }
  }
}

4. Check the new record via rails console

rails c
 DastSiteProfile.last
  DastSiteProfile Load (1.1ms)  SELECT "dast_site_profiles".* FROM "dast_site_profiles" ORDER BY "dast_site_profiles"."id" DESC LIMIT 1 
=> #<DastSiteProfile:0x0000000127b3f588
 id: 15,
 project_id: 20,
 dast_site_id: 9,
 created_at: Mon, 28 Nov 2022 20:43:05.485958000 UTC +00:00,
 updated_at: Mon, 28 Nov 2022 20:43:05.485958000 UTC +00:00,
 name: "Test GraphQL",
 excluded_urls: [],
 auth_enabled: false,
 auth_url: nil,
 auth_username_field: nil,
 auth_password_field: nil,
 auth_username: nil,
 target_type: "api",
 scan_method: "graphql",
 auth_submit_field: nil,
 scan_file_path: "http://localhost">

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