Merge branch 'chore/87-write-documentation-to-explain-our-protocol' into 'main'

Documentation describing the structure and conventions of our network protocol

Closes #77 and #87

See merge request cs108-fs26/Gruppe-13!96

documents/docs/our-protocol.md

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+# Our Network Protocol Documentation
+
+## Overview
+Our protocol is inspired by *POP3*, but has been highly customized to fit our specific needs.
+It is a text-based protocol operating over raw TCP sockets, designed for human readability and strict structure.
+
+## Packet Structure
+Each network packet consists of:
+- **4-byte header**: Specifies the size of the payload (big-endian integer).
+- **4-byte request ID**: Generated by the client, used to match requests and responses.
+- **Payload**: The actual data, its size as specified by the header.
+
+This structure is used for both requests and responses.
+
+## Conventions
+- All keys (in both requests and responses) use UPPER_SNAKE_CASE.
+- Only a-z, A-Z, 0-9 are allowed in keys.
+- Only human-readable strings are transmitted.
+- Binary data is not allowed.
+
+## Request Format
+A request consists of a single line:
+
+```
+COMMAND KEY1=ARG1 KEY2=ARG2
+```
+
+- **COMMAND**: The action to perform.
+- **KEY=VALUE pairs**: Optional parameters. There may be zero or more.
+- **Whitespace**: Extra spaces between key, separator, and value are ignored. Any other characters between them are an error.
+- **Standalone values**: Not allowed. Every value must have a key.
+
+### String Values
+- Strings with spaces must be enclosed in single quotes: `'example string'`.
+- Inside quoted strings, line breaks are allowed.
+- To include a single quote inside a string, escape it (e.g., `'It\'s fine'`).
+
+If these rules are violated, the request is considered invalid and will be rejected.
+
+## Response Format
+Responses are more complex and can represent nested collections.
+
+- **Success**: Starts with `+OK`
+- **Error**: Starts with `-ERR`
+- After the status, a newline follows, then fields in the format `KEY=VALUE`.
+- Collections and elements are ended with the `END` keyword.
+- A collection starts with a key, and its elements are indented.
+- A element starts with a key, and its fields are indented.
+
+### Example: Nested Collection
+```
++OK
+    KEY1=VALUE1
+    FIELDS
+        FIELD
+            NESTED_KEY=NESTED_VALUE
+        END
+    END
+    KEY2=VALUE2
+END
+```
+
+## Error Handling
+Any violation of the format (invalid characters, unescaped quotes, binary data, etc.) results in the request being rejected with an error response.
+
+### Example Error Response When Violating Syntax Rules:
+```
+-ERR
+    CODE=PARSING_ERROR
+    MSG='Error occured during parsing. Likely due to malformed payload.'
+END
+```