feat: add admin module + add validation for claiming structures

src/admin/admin.controller.spec.ts

src/admin/admin.controller.ts

src/admin/admin.module.ts

src/admin/admin.service.spec.ts

src/admin/admin.service.ts

src/admin/dto/pending-structure.dto.ts

src/app.module.ts

src/configuration/config.ts

src/mailer/mail-templates/adminStructureClaim.ejs

src/mailer/mail-templates/adminStructureClaim.json

src/structures/structures.controller.ts

src/structures/structures.service.ts

src/users/users.controller.ts

src/users/users.service.ts