Add a space between the subject prefix and the subject

Co-authored-by: Stephen Margheim <[email protected]>

Author: francescob

app/mailers/solid_errors/error_mailer.rb

@@ -5,7 +5,9 @@ def error_occurred(occurrence)
       @occurrence = occurrence
       @error = occurrence.error
       subject = "#{@error.severity_emoji} #{@error.exception_class}"
-      subject.prepend(SolidErrors.email_subject_prefix) if SolidErrors.email_subject_prefix.present?
+      if SolidErrors.email_subject_prefix.present?
+        subject = [SolidErrors.email_subject_prefix, subject].join(" ").squish!
+      end
       mail(
         subject: subject,
         from: SolidErrors.email_from,