Modify the checkout widget to support subscriptions. Add usage-based billing toggle to sharing settings.

svelte/src/home_page/GetStarted.svelte

@@ -8,24 +8,21 @@ import Euro from "util/Euro.svelte";
 {#if $user !== null}
 	<div class="page_content">
 		<section>
-			{#if $user.subscription.type === "patreon"}
+			{#if $user.subscription.id !== ""}
 				<p>
-					You already have a Patreon subscription active. You cannot use
-					Prepaid while that subscription is active.
+					You already have the {$user.subscription.name} plan active.
+					Your account balance is <Euro
+					amount={$user.balance_micro_eur}/>. Subscriptions are
+					charged from this balance every day, use the form below to
+					top it up or to switch to another plan.
 				</p>
-			{:else if $user.subscription.type === "prepaid"}
-				<p>
-					You already have a Prepaid subscription active. Your account
-					balance is <Euro amount={$user.balance_micro_eur}/>. Use
-					the form below to top up your balance.
-				</p>
-				<Checkout/>
 			{:else}
 				<p>
-					Pick one of the subscription plans above to upgrade your
-					account to premium.
+					Pick a subscription plan to upgrade your account. Your
+					account balance is <Euro amount={$user.balance_micro_eur}/>.
 				</p>
 			{/if}
+			<Checkout/>
 		</section>
 	</div>
 {:else}