automatically create an identity on the first page (and other UI tweaks)

src/views/ImportAccountView.vue

@@ -36,17 +36,28 @@
       Enter a custom derivation path
       <input
         type="text"
-        class="block w-full rounded border border-slate-400 mb-4 px-3 py-2"
+        class="block w-full rounded border border-slate-400 mb-2 px-3 py-2"
         v-model="derivationPath"
       />
-      For previous uPort or Endorser users,
-      <a @click="derivationPath = UPORT_DERIVATION_PATH" class="text-blue-500">
-        click here to use that value.
-      </a>
+      <span class="ml-4">
+        For previous uPort or Endorser users,
+        <a
+          @click="derivationPath = UPORT_DERIVATION_PATH"
+          class="text-blue-500"
+        >
+          click here to use that value.
+        </a>
+      </span>
+
+      <div class="mt-4" v-if="numAccounts == 1">
+        <input type="checkbox" class="mr-2" v-model="shouldErase" />
+        <label>Erase the previous identifier.</label>
+      </div>
     </div>
+
     <div class="mt-8">
       <button
-        @click="from_mnemonic()"
+        @click="fromMnemonic()"
         class="block w-full text-center text-lg font-bold uppercase bg-blue-600 text-white px-2 py-3 rounded-md mb-2"
       >
         Import
@@ -89,16 +100,23 @@ export default class ImportAccountView extends Vue {
 
   mnemonic = "";
   address = "";
+  numAccounts = 0;
   privateHex = "";
   publicHex = "";
   derivationPath = DEFAULT_ROOT_DERIVATION_PATH;
   showAdvanced = false;
+  shouldErase = false;
+
+  async created() {
+    await accountsDB.open();
+    this.numAccounts = await accountsDB.accounts.count();
+  }
 
   public onCancelClick() {
     this.$router.back();
   }
 
-  public async from_mnemonic() {
+  public async fromMnemonic() {
     const mne: string = this.mnemonic.trim().toLowerCase();
     try {
       [this.address, this.privateHex, this.publicHex] = deriveAddress(
@@ -114,6 +132,9 @@ export default class ImportAccountView extends Vue {
       );
 
       await accountsDB.open();
+      if (this.shouldErase) {
+        await accountsDB.accounts.clear();
+      }
       await accountsDB.accounts.add({
         dateCreated: new Date().toISOString(),
         derivationPath: this.derivationPath,