Make donation amounts a customisable setting

config/locales/client.en.yml

@@ -15,6 +15,10 @@ en:
     discourse_donations_enable_transaction_fee: "Give the user the option of including the Stripe transaction fee in their donation."
     discourse_donations_transaction_fee_fixed: "Fixed part of Stripe transaction fee (changes per region). See <a href='https://stripe.com/pricing'>Stripe's pricing for your region</a> and <a href='https://support.stripe.com/questions/can-i-charge-my-stripe-fees-to-my-customers'>Stripe's explaination of passing fees onto customers</a>."
     discourse_donations_transaction_fee_percent: "Percent part of Stripe transaction fee (changes per region). See <a href='https://stripe.com/pricing'>Stripe's pricing for your region</a> and <a href='https://support.stripe.com/questions/can-i-charge-my-stripe-fees-to-my-customers'>Stripe's explaination of passing fees onto customers</a>."
+    discourse_donations_amounts: "Donation amounts available to user"
+    discourse_donations_custom_amount: "Allow custom donation amount"
+    errors:
+      discourse_donations_amount_must_be_number: "Amounts must be numbers"
 
   js:
     discourse_donations:

config/settings.yml

@@ -44,3 +44,9 @@ plugins:
   discourse_donations_transaction_fee_percent:
     client: true
     default: 0.029
+  discourse_donations_amounts:
+    client: true
+    type: list
+    default: '1|2|5|10|20|50'
+    regex: "^[0-9\\|]+$"
+    regex_error: "site_settings.errors.discourse_donations_amount_must_be_number"