Provide discounts for members for OAI-certified trainings

[dret]

For API Days Paris the current plan is to have three or four full-day trainings around various OpenAPI topics. These would be paid trainings, and they would issue "official" OAI certificates such as:

• OAI Advanced OpenAPI
• OAI API Product Management
• OAI Practical OpenAPI

Members should get significant discounts on these trainings which have to be arranged in advance with our training partner (in this case, API Days).