Database Scalability Working Group Pattern: Time Decay

Create a blueprint for the "Time Decay" pattern discussed in the context of the Database Scalability Working Group.

Expected content:

1. Describe what Time-Decay data is and what problems arise from it today.
2. Characteristics of time-decay data
3. Detail solution: Time-Decay data strategies
   1. Partitioning
   2. Pruning old data
   3. Moving old data outside of the database
4. Use cases with detailed examples
   1. Audit Events
   2. Web hook logs
   3. CI tables

May 7 - Confidence level of delivering by due date 50%

Related MR: gitlab-com/www-gitlab-com!79193 (merged)