Add exercise `ownership`'s subject and test

rust/tests/ownership_test/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "ownership"
+version = "0.1.0"
+
+[[package]]
+name = "ownership_test"
+version = "0.1.0"
+dependencies = [
+ "ownership",
+]

rust/tests/ownership_test/Cargo.toml

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+[package]
+name = "ownership_test"
+version = "0.1.0"
+authors = ["Augusto <aug.ornelas@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+ownership = { path = "../../../../rust-piscine-solutions/ownership"}

rust/tests/ownership_test/src/main.rs

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+/*
+## ownership
+
+### Instruction
+
+Create a function that takes ownership of a string and returns the
+first sub-word in it. It should work for camelCase as well as snake_case
+first_subword(camelCase) returns camel
+first_subword(snake_case) returns snake
+
+And fix the printing expression so the code works
+
+###
+*/
+
+use ownership::*;
+
+fn main() {
+	let s1 = String::from("helloWorld");
+	let s2 = String::from("snake_case");
+	let s3 = String::from("CamelCase");
+	let s4 = String::from("just");
+
+	println!("first_subword({}) = {}", s1.clone(), first_subword(s1)); // Must print first_subword(helloWorld) = hello
+	println!("first_subword({}) = {}", s2.clone(), first_subword(s2)); // Must print first_subword(snake_case) = snake
+	println!("first_subword({}) = {}", s3.clone(), first_subword(s3)); // Must print first_subword(CamelCase) = Camel
+	println!("first_subword({}) = {}", s4.clone(), first_subword(s4)); // Must print first_subword(just) = just
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+
+	#[test]
+	fn first_subword_test() {
+		struct TstString<'a> {
+			str: String,
+			l: &'a str,
+		}
+
+		let o_tsts = vec![
+			TstString {
+				str: "helloWorld".to_string(),
+				l: "hello",
+			},
+			TstString {
+				str: "how_you".to_string(),
+				l: "how",
+			},
+			TstString {
+				str: "Changeyou".to_string(),
+				l: "Changeyou",
+			},
+			TstString {
+				str: "CamelCase".to_string(),
+				l: "Camel",
+			},
+		];
+
+		for t in o_tsts.iter() {
+			assert_eq!(t.l.to_string(), first_subword(t.str.clone()));
+		}
+	}
+}

subjects/ownership/README.md

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+## ownership
+
+### Instruction
+
+- Create a function that takes ownership of a string and returns the first sub-word in it
+
+- It should work for `camelCase` as well as `snake_case`
+
+### Expected Function
+
+```rust
+pub fn first_subword(mut s: String) -> String {
+}
+```
+
+### Usage
+
+Here is a program to test your function
+
+```rust
+fn main() {
+	let s1 = String::from("helloWorld");
+	let s2 = String::from("snake_case");
+	let s3 = String::from("CamelCase");
+	let s4 = String::from("just");
+
+	println!("first_subword({}) = {}", s1.clone(), first_subword(s1)); 
+	println!("first_subword({}) = {}", s2.clone(), first_subword(s2));
+	println!("first_subword({}) = {}", s3.clone(), first_subword(s3));
+	println!("first_subword({}) = {}", s4.clone(), first_subword(s4));
+}
+```
+
+And its output
+
+```console
+student@ubuntu:~/[[ROOT]]/test$ cargo run
+first_subword(helloWorld) = hello
+first_subword(snake_case) = snake
+first_subword(CamelCase) = Camel
+first_subword(just) = just
+student@ubuntu:~/[[ROOT]]/test$
+```