Feature/optional redis - #13

Dereference of a possibly null reference.

Possible null reference argument for parameter 'identifier' in 'Task TenantManagementService.UpdateRegistrationSettingsAsync(string identifier, int registrationMode, string? allowedEmailDomains, string? allowedEmails, string? approvalFormFields, string? approvalInstructions, string? defaultApprovedRoles, CancellationToken cancellationToken = default(CancellationToken))'.

Possible null reference argument for parameter 'identifier' in 'Task TenantManagementService.UpdateEmailRestrictionSettingsAsync(string identifier, bool restrictEmailLogin, string? allowedEmailDomains, string? allowedEmails, CancellationToken cancellationToken = default(CancellationToken))'.

Possible null reference argument for parameter 'identifier' in 'Task TenantManagementService.UpdateLoanSettingsAsync(string identifier, int loanPeriodDays, int maxLoansPerUser, bool enableOverdueNotification, CancellationToken cancellationToken = default(CancellationToken))'.

Possible null reference argument for parameter 'identifier' in 'Task TenantManagementService.UpdateOidcSettingsAsync(string identifier, string? authority, string? clientId, string? clientSecret, string? roleClaimName = null, CancellationToken cancellationToken = default(CancellationToken))'.

Possible null reference argument for parameter 'identifier' in 'Task TenantManagementService.DeleteTenantAsync(string identifier, CancellationToken cancellationToken = default(CancellationToken))'.

Possible null reference assignment.

Possible null reference assignment.

Possible null reference assignment.