Add band and venue follows with concert diary

app/templates/new_concert.html

@@ -170,6 +170,13 @@
 
             </p>
 
+            <p>
+                <label for="band-names">Bands / Line-up <small>(eine Band pro Zeile)</small><br>
+                    <textarea id="band-names" name="band_names" rows="3" maxlength="4000" placeholder="dArtagnan&#10;Supportband"></textarea>
+                </label>
+                <small>Der Veranstaltungstitel bleibt frei. Diese Namen werden einzeln für „Band folgen“ verwendet.</small>
+            </p>
+
             <!-- ================================================= -->
             <!-- Veranstaltungsort -->
             <!-- ================================================= -->
@@ -895,6 +902,7 @@ flyerInput.addEventListener(
 // Originaldateien verarbeiten.
 const concertForm = flyerInput.form;
 const artistInput = document.getElementById("artist");
+const bandNamesInput = document.getElementById("band-names");
 const startDatetimeInput = document.getElementById("start-datetime");
 const duplicateWarning = document.getElementById("duplicate-warning");
 const duplicateConfirmed = document.getElementById("duplicate-confirmed");
@@ -934,7 +942,7 @@ async function checkForDuplicates(showWarning = true) {
     if (duplicateRequestController) duplicateRequestController.abort();
     duplicateRequestController = new AbortController();
     try {
-        const params = new URLSearchParams({artist, start_date: startDate});
+        const params = new URLSearchParams({artist, start_date: startDate, band_names: bandNamesInput.value});
         const response = await fetch(`/api/concerts/duplicates?${params}`, {
             signal: duplicateRequestController.signal
         });
@@ -948,7 +956,7 @@ async function checkForDuplicates(showWarning = true) {
     }
 }
 
-[artistInput, startDatetimeInput].forEach(input => input.addEventListener("input", () => {
+[artistInput, bandNamesInput, startDatetimeInput].forEach(input => input.addEventListener("input", () => {
     duplicateConfirmed.value = "false";
     concertForm.dataset.readyToSubmit = "false";
     clearTimeout(duplicateTimeout);