Remove unnecessary typehints

src/Contracts/Syncable.php

@@ -8,7 +8,7 @@ interface Syncable
 {
     public function getGlobalIdentifierKeyName(): string;
 
-    public function getGlobalIdentifierKey(): string;
+    public function getGlobalIdentifierKey();
 
     public function getCentralModelName(): string;
 

src/Contracts/Tenant.php

@@ -17,7 +17,7 @@ interface Tenant
     public function getTenantKeyName(): string;
 
     /** Get the value of the key used for identifying the tenant. */
-    public function getTenantKey(): ?string;
+    public function getTenantKey();
 
     /** Get the value of an internal key. */
     public function getInternal(string $key);

src/Database/Models/Tenant.php

@@ -37,7 +37,7 @@ class Tenant extends Model implements Contracts\Tenant
         return 'id';
     }
 
-    public function getTenantKey(): ?string
+    public function getTenantKey()
     {
         return $this->getAttribute($this->getTenantKeyName());
     }

tests/ResourceSyncingTest.php

@@ -603,7 +603,7 @@ class CentralUser extends Model implements SyncMaster
         return ResourceUser::class;
     }
 
-    public function getGlobalIdentifierKey(): string
+    public function getGlobalIdentifierKey()
     {
         return $this->getAttribute($this->getGlobalIdentifierKeyName());
     }
@@ -636,7 +636,7 @@ class ResourceUser extends Model implements Syncable
     protected $guarded = [];
     public $timestamps = false;
 
-    public function getGlobalIdentifierKey(): string
+    public function getGlobalIdentifierKey()
     {
         return $this->getAttribute($this->getGlobalIdentifierKeyName());
     }

tests/TenantModelTest.php

@@ -224,7 +224,7 @@ class AnotherTenant extends Model implements Contracts\Tenant
         return 'id';
     }
 
-    public function getTenantKey(): string
+    public function getTenantKey()
     {
         return $this->getAttribute('id');
     }