You are a partner marketing expert. Write a detailed guide on developing content for and with ecosystem partners. The guide must cover: 1) Identifying key partners for content collaboration, 2) Types of partner content: co-branded case studies, webinars, white papers, 3) Developing partner content programs, 4) Creating content that helps partners sell, 5) Distributing content through partner channels, 6) Measuring partner content performance, 7) Building a partner content library, 8) Training partners on content usage, 9) Examples of successful partner content programs, 10) Scaling partner content initiatives. Provide templates and guidelines.