Add LocationProvider service with mock data

src/main/kotlin/org/jetbrains/plugins/template/weatherApp/services/LocationsProvider.kt

@@ -0,0 +1,32 @@
+package org.jetbrains.plugins.template.weatherApp.services
+
+import com.intellij.openapi.components.Service
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import org.jetbrains.plugins.template.weatherApp.model.Location
+
+@Service
+internal class LocationsProvider : SearchAutoCompletionItemProvider<Location> {
+    private val locationStateFlow = MutableStateFlow(
+        listOf(
+            Location("Munich", "Germany"),
+            Location("Belgrade", "Serbia"),
+            Location("Berlin", "Germany"),
+            Location("Rome", "Italy"),
+            Location("Paris", "France"),
+            Location("Sydney", "Australia"),
+            Location("Moscow", "Russia"),
+            Location("Tokyo", "Japan"),
+            Location("New York", "USA"),
+        )
+    )
+
+    fun provideLocations(): StateFlow<List<Location>> = locationStateFlow.asStateFlow()
+
+    override fun provideSearchableItems(searchTerm: String): List<Location> {
+        return locationStateFlow
+            .value
+            .filter { it.isSearchApplicable(searchTerm) }
+    }
+}

src/main/kotlin/org/jetbrains/plugins/template/weatherApp/services/SearchAutoCompletionItemProvider.kt

@@ -0,0 +1,16 @@
+package org.jetbrains.plugins.template.weatherApp.services
+
+import org.jetbrains.plugins.template.weatherApp.model.Searchable
+
+/**
+ * Defines a provider interface for auto-completion items based on a search query.
+ *
+ * Implementations of this interface are responsible for supplying a filtered list of
+ * items that match the given search term. These items must conform to the [Searchable] interface,
+ * which ensures that they can be evaluated against the query.
+ *
+ * @param T The type of items provided by this interface, which must extend [Searchable].
+ */
+internal interface SearchAutoCompletionItemProvider<T : Searchable> {
+    fun provideSearchableItems(searchTerm: String): List<T>
+}