Adds validation and error handling to signup

src/main/kotlin/net/halfbinary/scavengerhuntapi/service/SignupService.kt

@@ -1,13 +1,22 @@
 package net.halfbinary.scavengerhuntapi.service
 
+import net.halfbinary.scavengerhuntapi.error.exception.InvalidEmailException
+import net.halfbinary.scavengerhuntapi.error.exception.PreexistingAccountException
 import net.halfbinary.scavengerhuntapi.model.converter.toRecord
 import net.halfbinary.scavengerhuntapi.model.domain.Hunter
 import net.halfbinary.scavengerhuntapi.repository.HunterRepository
+import org.apache.commons.validator.routines.EmailValidator
 import org.springframework.stereotype.Service
 
 @Service
 class SignupService(private val hunterRepository: HunterRepository) {
     fun createNewHunter(hunter: Hunter) {
+        if (!EmailValidator.getInstance().isValid(hunter.email)) {
+            throw InvalidEmailException(hunter.email)
+        }
+        if (hunterRepository.findByEmail(hunter.email) != null) {
+            throw PreexistingAccountException()
+        }
         hunterRepository.save(hunter.toRecord())
     }
 }