Debug log updates, error message updates on curl failure

Config setup works with null data if no data is set.

Debugger is now launched in the AamzonIncentive class at the beginning
Debugger id/debug flag set is now one static call
Debugger methods all have proper PHPdoc documentationn added

Fixed Client/Curl error messages to include the original error message
too. Also made sure that a possible null endpoint is not throwing errors

src/Amazon/Config/Config.php

@@ -80,9 +80,9 @@ class Config implements ConfigInterface
 	}
 
 	/**
-	 * @return string
+	 * @return string|null
 	 */
-	public function getEndpoint(): string
+	public function getEndpoint(): ?string
 	{
 		return $this->endpoint;
 	}
@@ -100,9 +100,9 @@ class Config implements ConfigInterface
 	}
 
 	/**
-	 * @return string
+	 * @return string|null
 	 */
-	public function getAccessKey(): string
+	public function getAccessKey(): ?string
 	{
 		return $this->access_key;
 	}
@@ -119,9 +119,9 @@ class Config implements ConfigInterface
 	}
 
 	/**
-	 * @return string
+	 * @return string|null
 	 */
-	public function getSecret(): string
+	public function getSecret(): ?string
 	{
 		return $this->secret_key;
 	}
@@ -138,9 +138,9 @@ class Config implements ConfigInterface
 	}
 
 	/**
-	 * @return string
+	 * @return string|null
 	 */
-	public function getCurrency(): string
+	public function getCurrency(): ?string
 	{
 		return $this->currency;
 	}
@@ -158,9 +158,9 @@ class Config implements ConfigInterface
 	}
 
 	/**
-	 * @return string
+	 * @return string|null
 	 */
-	public function getPartner(): string
+	public function getPartner(): ?string
 	{
 		return $this->partner_id;
 	}
@@ -177,9 +177,9 @@ class Config implements ConfigInterface
 	}
 
 	/**
-	 * @return bool
+	 * @return bool|null
 	 */
-	public function getDebug(): bool
+	public function getDebug(): ?bool
 	{
 		return $this->debug;
 	}