Add client assertion authentication

[Dongle (dongle-the-gadget)]

Add support for MSAL Client Assertion authentication. Client Assertion authentication enables users to use GitHub Actions OpenID Connect, which is a more secure way to authenticate to Microsoft services without requiring client secrets.

The Client Assertion mechanism is activated by using the --clientAssertion option in the reconfigure command:

msstore reconfigure --clientId [Client ID] --clientAssertion [OIDC JWT] [other options]

A GitHub workflow that utilizes OpenID Connect might look something like this:

permissions:
  contents: read
  id-token: write

jobs:
  publish:
    runs-on: windows-latest

    steps:
      - name: Login
        run: |
          $oidcToken = ConvertTo-SecureString "$env:ACTIONS_ID_TOKEN_REQUEST_TOKEN" -AsPlainText -Force
          $assertion = Invoke-RestMethod -Uri "$env:ACTIONS_ID_TOKEN_REQUEST_URL&audience=api://AzureADTokenExchange" -Authentication Bearer -Token $oidcToken
          msstore reconfigure --sellerId ${{ secrets.SELLER_ID }} --clientId ${{ secrets.CLIENT_ID }} --clientAssertion $assertion.value --tenantId ${{ secrets.TENANT_ID }}
      - name: Publish
        run: msstore publish example.msix -id <Store App ID>