Binary / base64 field automatic encoding and eager loading

[joshwlewis]

This PR adds automatic support for base64 / binary content, and is supported by the changes to type signatures in forcedotcom/sf-fx-sdk-nodejs#141.

The additional functionality has two parts:

• Population of the binaryFields property by eager-loading binary content during queries.
• Automatic base64 encoding of the values in binaryFields when performing upstream record modification.

An example function leveraging this new functionality might look like this:

import { InvocationEvent, Context, Logger, Record, RecordModificationResult } from "sf-fx-sdk-nodejs";
import sharp from 'sharp';

/**
 * thumber queries an org for images matching a title, then creates a 50px png
 * thumbnail of each image, and uploads each thumbnail as a new image.
 */

export default async function thumber(event: InvocationEvent<any>, context: Context, logger: Logger):
    Promise<PromiseSettledResult<RecordModificationResult>[]> {

    const queryResult = await context.org.dataApi
        .query(`SELECT Id, Title, VersionData FROM ContentVersion WHERE Title = '${event.data.title}' AND FileExtension IN ('svg', 'png', 'jpg')`);

    return await Promise.allSettled(queryResult.records.map((record) => createThumb(context, record)));
}

async function createThumb(context: Context, record: Record): Promise<RecordModificationResult> {
  const resizedData = await sharp(record.binaryFields.versiondata)
    .resize(50)
    .png()
    .toBuffer();
  return await context.org.dataApi.create({
    type: "ContentVersion",
    binaryFields: {
      VersionData: resizedData,
    },
    fields: {
      Title: `${record.fields.title}-thumbnail`,
      PathOnClient: `${record.fields.title}-thumnail.png`,
      Description: `Thumbnail generated from file ${record.fields.id}`,
    }
  });
}

GUS-W-11543492