implemented purpose proposals based on source, dest and amount

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

frontend/src/routes/accounting/add_entry.svelte

@@ -42,7 +42,10 @@
 	}
 
 	function focusOnEnter(ev,id){
-		if (ev.key == 'Enter') document.getElementById(id).focus();
+		if (ev.key == 'Enter') {
+			proposePurpose();
+			document.getElementById(id).focus();
+		}
 	}
 
 	async function getAccountTags(text){
@@ -93,6 +96,20 @@
 		}
 	}
 
+	async function proposePurpose(){
+		const source      = entry.source;
+		const destination = entry.destination;
+		const amount      = entry.amount;
+		const url         = api(`accounting/${account.id}/purposes`);
+		const res         = await post(url,{source,destination,amount});
+		if (res.ok) {
+			yikes();
+			var lastTransaction = await res.json();
+			entry.purpose       = { display: lastTransaction.purpose};
+			entry.tags          = lastTransaction.tags;
+		} else error(res);
+	}
+
 	async function save(){
 		let data = {
 			...entry,
@@ -169,4 +186,4 @@
 	<span>
 		<button onclick={save}>{t('save')}</button>
 	</span>
-</fieldset>
+</fieldset>