Design the DB schema

[Nicolas-Hermet]

Why ?\r\n\r\nWe have to get a good first draft of our DB. Often, you'll have to create one from only a discussion with a client/product and this task is here to reflect this process.\r\n\r\n### What the project is ?\r\n\r\nThe project goal is to give an interface for lessons at THP. We have 2 persona:\r\n* Teachers: host there lessons and get feedback, either instantly or afterwards.\r\n* Students: participate to lessons and give feedback during the class.\r\n\r\nWe want:\r\n* The teacher must be able to create a class once and create a new instance of it each time he gives the same lesson;\r\n* A teacher must be able to invite anyone on a lesson;\r\n* A class should have a list of steps containing a title and a description (not too long);\r\n* A student will be able to tick a step for a lesson as soon as the notion is understood;\r\n* A student should be able to add a new question on a lesson;\r\n* A student should be able to vote for a question (but not more than once);\r\n* There must be only one table of users. A student and a teacher have this role depending on what they do for a particular lesson.\r\n\r\n\r\n### Must have\r\n- [ ] A database schema (if you don't have any preference to create it, draw.io work but is probably not optimal)\r\n- [ ] Have someone who reviewed your decisions\r\n