E-Sender Service. Web mvc app move to web api api

[live-dev999]

• Remove views for mailsender
• Inherit from ControllerBase instead of Controller
• Use ApiController attribute to save us some manual work(.SetCompatibilityVersion.Version_2_2);
• Replace AddMvc with AddMvcCore and make the necessary adjustments
• Remove NotFound on entity update, as it's not doing anything with our current service update implementation
• Create exception filter to handle concurrent update errors
• Add a delete endpoint
• implement the board