Improve Azure AD documentation

[Silex]

Hello,

Don't merge this blindly we need to discuss some commits:

1. Should we really remove docs/integrations/identity-providers/self-hosted/azure-ad.md? Looked outdated to me but maybe it's still useful.
2. Is step 5 really outdated? I removed it because I cannot do what it says as accessTokenAcceptedVersion is nowhere to be found (see manifest below).
3. In "Step 6: Generate client secret" we don't talk about the secret expiration, which is 6 months by default. Is 6 months a safe value? What will happen when the secret expire?

Here's my manifest (anonymized):

{
    "id": "11111111-2222-3333-4444-555555555555",
    "deletedDateTime": null,
    "appId": "11111111-2222-3333-4444-555555555555",
    "applicationTemplateId": null,
    "disabledByMicrosoftStatus": null,
    "createdDateTime": "2025-02-13T15:18:02Z",
    "displayName": "Netbird",
    "description": null,
    "groupMembershipClaims": null,
    "identifierUris": [
	"api://11111111-2222-3333-4444-555555555555"
    ],
    "isDeviceOnlyAuthSupported": null,
    "isFallbackPublicClient": true,
    "nativeAuthenticationApisEnabled": null,
    "notes": null,
    "publisherDomain": "domain.com",
    "serviceManagementReference": null,
    "signInAudience": "AzureADMyOrg",
    "tags": [],
    "tokenEncryptionKeyId": null,
    "samlMetadataUrl": null,
    "defaultRedirectUri": null,
    "certification": null,
    "optionalClaims": null,
    "requestSignatureVerification": null,
    "addIns": [],
    "api": {
	"acceptMappedClaims": null,
	"knownClientApplications": [],
	"requestedAccessTokenVersion": null,
	"oauth2PermissionScopes": [
	    {
		"adminConsentDescription": "Allows netbird to access and manage organization users",
		"adminConsentDisplayName": "Manage Organization Users",
		"id": "11111111-2222-3333-4444-555555555555",
		"isEnabled": true,
		"type": "User",
		"userConsentDescription": "Allows netbird to access and manage organization users",
		"userConsentDisplayName": "Manage Organization Users",
		"value": "api"
	    }
	],
	"preAuthorizedApplications": [
	    {
		"appId": "11111111-2222-3333-4444-555555555555",
		"delegatedPermissionIds": [
		    "11111111-2222-3333-4444-555555555555"
		]
	    }
	]
    },
    "appRoles": [],
    "info": {
	"logoUrl": null,
	"marketingUrl": null,
	"privacyStatementUrl": null,
	"supportUrl": null,
	"termsOfServiceUrl": null
    },
    "keyCredentials": [],
    "parentalControlSettings": {
	"countriesBlockedForMinors": [],
	"legalAgeGroupRule": "Allow"
    },
    "passwordCredentials": [
	{
	    "customKeyIdentifier": null,
	    "displayName": "Netbird",
	    "endDateTime": "2025-08-12T15:37:55.572Z",
	    "hint": "nXe",
	    "keyId": "11111111-2222-3333-4444-555555555555",
	    "secretText": null,
	    "startDateTime": "2025-02-13T16:37:55.572Z"
	}
    ],
    "publicClient": {
	"redirectUris": [
	    "http://localhost:53000"
	]
    },
    "requiredResourceAccess": [
	{
	    "resourceAppId": "11111111-2222-3333-4444-555555555555",
	    "resourceAccess": [
		{
		    "id": "11111111-2222-3333-4444-555555555555",
		    "type": "Scope"
		},
		{
		    "id": "11111111-2222-3333-4444-555555555555",
		    "type": "Role"
		}
	    ]
	},
	{
	    "resourceAppId": "11111111-2222-3333-4444-555555555555",
	    "resourceAccess": [
		{
		    "id": "11111111-2222-3333-4444-555555555555",
		    "type": "Scope"
		}
	    ]
	}
    ],
    "verifiedPublisher": {
	"displayName": null,
	"verifiedPublisherId": null,
	"addedDateTime": null
    },
    "web": {
	"homePageUrl": null,
	"logoutUrl": null,
	"redirectUris": [],
	"implicitGrantSettings": {
	    "enableAccessTokenIssuance": true,
	    "enableIdTokenIssuance": true
	},
	"redirectUriSettings": []
    },
    "servicePrincipalLockConfiguration": {
	"isEnabled": true,
	"allProperties": true,
	"credentialsWithUsageVerify": true,
	"credentialsWithUsageSign": true,
	"identifierUris": false,
	"tokenEncryptionKeyId": true
    },
    "spa": {
	"redirectUris": [
	    "https://netbird.domain.com/auth",
	    "https://netbird.domain.com/silent-auth"
	]
    }
}

[Silex]

@mlsmaycon there's no rush for this PR but can you answer question 3 about the client secret? Should I use one that never expires? What happens when it expire, all my clients cannot connect?