Post a Batch of Feed Elements with a New (Binary) File

trigger postFeedItemToAccountWithBinary on Account (after insert) {
    Account[] accounts = Trigger.new;
    
    // Bulk post to the account feeds.

    List<ConnectApi.BatchInput> batchInputs = new List<ConnectApi.BatchInput>();

    for (Account a : accounts) {
        ConnectApi.FeedItemInput input = new ConnectApi.FeedItemInput();

        input.subjectId = a.id;
        
        ConnectApi.MessageBodyInput body = new ConnectApi.MessageBodyInput();
        body.messageSegments = new List<ConnectApi.MessageSegmentInput>();

        ConnectApi.TextSegmentInput textSegment = new ConnectApi.TextSegmentInput();
        textSegment.text = 'Let\'s win the ' + a.name + ' account.';

        body.messageSegments.add(textSegment);
        input.body = body;

        ConnectApi.ContentCapabilityInput contentInput = new ConnectApi.ContentCapabilityInput();
        contentInput.title = 'Title';

        ConnectApi.FeedElementCapabilitiesInput capabilities = new ConnectApi.FeedElementCapabilitiesInput();
        capabilities.content = contentInput;

        input.capabilities = capabilities;

        String text = 'We are words in a file.';
        Blob myBlob = Blob.valueOf(text);
        ConnectApi.BinaryInput binInput = new ConnectApi.BinaryInput(myBlob, 'text/plain', 'fileName');

        ConnectApi.BatchInput batchInput = new ConnectApi.BatchInput(input, binInput);

        batchInputs.add(batchInput);
    }

    ConnectApi.ChatterFeeds.postFeedElementBatch(Network.getNetworkId(), batchInputs);