docs: OAuth Features

[maduvena]

Docs under the head admin/auth-server/oauth-features

• [x] docs: 'Authorization Code Grant': 'admin/auth-server/oauth-features/auth-code-grant.md'
• [x] docs: 'Implicit Grant': 'admin/auth-server/oauth-features/implicit-grant.md'
• [ ] docs: 'Password Grant': 'admin/auth-server/oauth-features/password-grant.md'
• [ ] docs: 'Device Grant': 'admin/auth-server/oauth-features/device-grant.md'
• [x] docs: 'Client Credential Grant': 'admin/auth-server/oauth-features/client-credential-grant.md'
• [ ] docs: 'PKCE': 'admin/auth-server/oauth-features/pkce.md'
• [ ] docs: 'DPoP': 'admin/auth-server/oauth-features/dpop.md'
• [ ] docs: 'MTLS': 'admin/auth-server/oauth-features/mtls.md'
• [ ] docs: 'PAR': 'admin/auth-server/oauth-features/par.md'

[ossdhaval]

Hi @maduvena, should we add refresh token and UMA Ticket grants to the list?

[ossdhaval]

Closing this issue as now we have individual issues to track the completion of each document.