Move errors to new common package, improve test coverage script

bin/test_coverage.sh

@@ -1,11 +1,12 @@
 pushd $(dirname "$0")/.. # run from root dir
 
-set -e
+rm -rf ./coverage
+mkdir ./coverage/
 
 go build -cover -o target/pilgrim_coverage main.go
 
 chmod 777 ./target/pilgrim_coverage
-GOCOVERDIR=coverage ./target/pilgrim
+GOCOVERDIR=coverage ./target/pilgrim_coverage
 
 go tool covdata percent -i=coverage
 

internal/pilgrim_common/error.go

@@ -1,4 +1,8 @@
-package pilgrim_conf
+package pilgrim_common
+
+type PilgrimError interface {
+	error
+}
 
 type pilgrimValidationError struct {
 	validationError string

internal/pilgrim_conf/context.go

@@ -2,6 +2,8 @@ package pilgrim_conf
 
 import (
 	"log"
+
+	"mvvasilev.dev/pilgrim/internal/pilgrim_common"
 )
 
 const DefaultMigrationDirectory = "./migrations"
@@ -143,7 +145,7 @@ func determineMigrationPhaseAndScript(cli MigrationPhaseRetriever) (phase Migrat
 	_, isDownProvided := cli.IsDown()
 
 	if (!isUpProvided && !isDownProvided) || (isUpProvided && isDownProvided) {
-		return MigrationPhase_Down, EmptyString, PilgrimInvalidError("Must provide either --up or --down, but not both.")
+		return MigrationPhase_Down, EmptyString, pilgrim_common.PilgrimInvalidError("Must provide either --up or --down, but not both.")
 	}
 
 	if isUp {

internal/pilgrim_conf/url_parts.go

@@ -6,6 +6,8 @@ import (
 	"regexp"
 	"slices"
 	"strings"
+
+	"mvvasilev.dev/pilgrim/internal/pilgrim_common"
 )
 
 const EmptyString = ""
@@ -135,7 +137,7 @@ func ParseArguments(arguments string) map[string]string {
 // Returns true if valid, with nil error, or false if invalid, with the validation error
 func (urlParts *UrlParts) Validate() (bool, error) {
 	if !slices.Contains(AvailableDbDrivers, DbDriver(urlParts.Driver)) {
-		return false, PilgrimInvalidError(fmt.Sprintf("URLParts invalid: Provided driver %v is not currently supported ( must be one of %v )", urlParts.Driver, AvailableDbDrivers))
+		return false, pilgrim_common.PilgrimInvalidError(fmt.Sprintf("URLParts invalid: Provided driver \"%v\" is not currently supported ( must be one of %v )", urlParts.Driver, AvailableDbDrivers))
 	}
 
 	return true, nil