Enhance Multitenancy Workflow

[iammukeshm]

Current Multitenant Implementation takes tenant details from AppSettings. It's better to have these settings stored in the Database and cache them to application memory.

• [x] Move to a Database Managed Tenant Approach.
• [x] Create a Root User who has access to manage tenants.
• [x] Root user should also be a tenant himself.
• [x] Introduce Caching in Tenant Service
• [x] Tenant Creation
• [x] Tenant Validity in Months -> after which tenant users won't have access to the system
• [x] Tenant Status - Active / Inactive
• [x] Only Root User has access to tenant management

The remaining flow remains the same as it is now.

[iammukeshm]

Work in Progress at branch https://github.com/fullstackhero/dotnet-webapi-boilerplate/tree/feature/better-multitenancy