add docs folder

Author: ythirion

docs/INSTRUCTIONS.md

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+## 🚀 D-1: Getting ready for your journey.
+
+The Advent of Craft 2023 starts tomorrow.
+
+A long journey awaits you.
+
+In order to prepare your ship for this journey, here is a task
+list of the things you need to know / install before setting sail.
+
+### 🔨Install your tools
+
+- Install an IDE. Intellij Community or VS Code should do.
+- Create an account on github to get the latest changes and fork the repository.
+- Install Git to get the repository. With a git bash or git client.
+- Install and create an account on Discord to share with the community.
+
+### ✅ The process
+
+Each day, an exercise is going to be posted at around 1PM Europe time (GMT+1) 
+in the public repository here:
+https://github.com/advent-of-craft/advent-of-craft.git
+
+At the same time, a solution for the exercise of the previous day 
+is going to be posted.
+
+The repository will have an _exercise/_ folder containing a subfolder for each day 
+as well as a _solution/_ folder with step-by-step instructions.
+
+### 👨‍💻Posting your solution
+
+Each day, a dedicated channel in the Discord is going to be created for posting solutions.
+
+We advise you to post your solution in order to benefit the whole community.
+You can use the following methods to do so:
+
+1) Post a screenshot of your solution in the Discord channel (via Codesnap or other tools).
+2) Post your code in a markdown format.
+   - You can wrap your code within this markdown
+   ```java
+      paste your code like this
+   ```
+3) From your github account you can create your own solution.
+   - you can fork the following repository: https://github.com/advent-of-craft/advent-of-craft.git
+   - post a link to your repository and solution in the Discord channel (can be with branches per day)
+
+We encourage everyone to start healthy discussions on the Discord that are related
+to the exercise of the day and any advice you want to share with the community.
+
+### ❓Help on your journey
+
+A help channel is available at any time on the Discord server.
+
+If you get stuck with IDE configuration, git commands or anything that prevents you
+from coding, please let us know, your hosts and the community will make everything
+possible to help you.
+
+### 🎙️Last word from your hosts
+
+Remember that this initiative is completely free, and you can reuse these exercises
+for your own crafting journey with the step-by-step solutions as well.
+
+> We humbly ask you in return to approach the journey with an open mind,
+a good will and that you respect the other passengers. The Discord is a safe
+space where all conversations are open so let's all remember to be civilized.
+
+We are all here to learn.
+
+🎅 May this epic crafting journey begin! 🧑‍🎄

docs/exercise/day01/challenge.md

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+## Day 1: code that is easy to understand.
+
+Welcome to the Advent of Craft 2023.
+
+We begin this journey by going over the basics. 
+We all do this everyday:
+
+_Reading a simple code._ 
+
+If you understand a piece of code quickly, 
+it does not mean the code is readable much less well-crafted.
+It also does not mean the code should not be refactored.
+
+A readable code is not always the fewest line or the one 
+that uses the latest framework technique.
+
+Think about the real value your code should bring.
+
+>**Challenge of day 1: Make your production code easier to understand.**
+
+May the crafting journey begin!
+
+- <u>💡HINT:</u> Your IDE is your best friend in this journey!
+
+![snippet of the day](snippet.png)
+
+### Proposed Solution
+[![Proposed Solution Guide](../../img/proposed-solution.png)](solution/step-by-step.md)

docs/exercise/day01/snippet.png

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+## Day 1: Make your production code easier to understand.
+
+### Encapsulate Conditionals
+
+If conditionals are too complex, it might hamper readability.
+
+1) Start by simplifying the code
+2) Extract method for each part of the condition
+3) Think deeply on the business to find names that represent it
+
+Your code should look more readable and as a result more maintainable.
+
+>**Tip of the day: the best documentation is the code itself.**
+
+### Share your experience
+
+How does your code look like? Anything you'd like to add?
+
+Please let everyone know in the discord.

docs/exercise/day01/solution/challenge-done.md

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+## Day 1: Make your production code easier to understand.
+### Encapsulate Conditionals
+If conditionals are too complex, it might hamper readability.
+
+- Start by simplifying the code
+
+![Simplify if else](img/simplify-if-else.png)
+
+- Then `Extract Method` for each part of the condition
+
+![Extract Method](img/extract-method.png)
+
+- Think deeply on the business to find names that represent it
+
+```java
+public record Food(LocalDate expirationDate,
+                   Boolean approvedForConsumption,
+                   UUID inspectorId) {
+    public boolean isEdible(Supplier<LocalDate> now) {
+        return isFresh(now) &&
+                canBeConsumed() &&
+                hasBeenInspected();
+    }
+
+    private boolean isFresh(Supplier<LocalDate> now) {
+        return this.expirationDate.isAfter(now.get());
+    }
+
+    private boolean hasBeenInspected() {
+        return this.inspectorId != null;
+    }
+
+    private Boolean canBeConsumed() {
+        return this.approvedForConsumption;
+    }
+}
+```
+
+- <u>⚠️ WARNING:</u> Make sure your tests are still passing throughout your refactoring!

docs/exercise/day01/solution/img/extract-method.png

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+## Day 2: Fight indentation.
+
+On the second day of your crafting journey, you are to meet your first fizzbuzz code. 
+You probably know this piece of code and yet there is so much in it to unpack.
+
+Today though your task is but a simple one: reducing the complexity of the code
+by removing as much indentation as you can.
+
+_Remember that a developer never forgets his craft. He just adds to it._
+
+>**Challenge of day 2: Your code can only have one level of indentation.**
+
+May your journey continue!
+
+- <u>💡HINT:</u> Apply what you learned on day 1
+
+![snippet of the day](snippet.png)
+
+### Proposed Solution
+[![Proposed Solution Guide](../../img/proposed-solution.png)](solution/step-by-step.md)