Updated SKY API Documentation

A new shared changelog was posted on 3/20/2020. See the changelog for more information.

We added and updated the following SKY API documentation.

• Added a new Developer account section on the Basics page. This section provides details about what it means to create a SKY Developer account and how to sign up for a Blackbaud ID. A Blackbaud ID is a prerequisite for a SKY Developer account.
• Updated information in the Subscription section on the Basics page.
• Added new information about increasing API quota limits to the Quotas section on the Basics page.
• Added a new landing page for Applications. For those who have applications or are interested in developing applications, this page provides overview and helpful information. As you have questions or need more details, we will expand this section.