[Feature] Meta - Add the Meta functions

[MariusStorhaug]

• Fix Authentication issues with DeviceFlow

  • Fixes [Bug] Auth - Issue with refresh when no access token #20
  • Fixes [Feature] Auth - Automatically detect if token is still valid for Device Flow #19
  • The Auth module now supports Device Flow for both GitHubApp, OAuthApp, PAT and System PAT.
    • If running Connect-GitHubAccount the flow will do the following:
      • If system tokens are available, use those to log in.
      • Else trigger device flow. Check if access token is valid. if token is valid for less than 4 hours, refresh the token using the device flow refresh token process. Same if access token is expired.
      • If refresh token is expired, trigger new device flow auth process.
      • If type of auth changes due to switchs, trigger new device flow auth process.
    • If running Connect-GitHubAccount -AccessToken is run, an interactive process is assumed. A prompt will ask the user to provide a PAT token, which can be both Fine grained or classic.
  • Changed so tokens are treated as SecureStrings from its stored until its put in the function/command that uses it, and converts it there.

• Fixes [Feature] Config - Rearchitect how vars are stored #23

  • Configuration is now stored with a prefix that is configured in the SecretVault.psd1 file in the data folder. Default this is "GHPS_". All settings written to the secret store uses this.

• Adds an API call method Invoke-GitHubAPI to manage all the calls to the GitHub API

  • Includes default usage of settings, like ApiBaseUri, AccessToken (now as a SecureString) and Version for the api version.
  • Supports pagination, in line with Using pagination in the REST API

• Fixes [Feature] Meta - Get meta information about GitHub #12

  • Adds functions under the Meta namespace.