feat: initial terraform provider for artifactapi v0.0.1

Resources:
- artifactapi_remote: CRUD for remote proxy repositories
- artifactapi_virtual: CRUD for virtual (merged) repositories

Data sources:
- data.artifactapi_remote: read remote config
- data.artifactapi_virtual: read virtual config

Supports all 10 package types (generic, docker, helm, pypi, npm,
rpm, alpine, puppet, terraform, goproxy), allowlist/blocklist,
tag banning, quarantine, and terraform import.

internal/provider/client.go

@@ -0,0 +1,93 @@
+package provider
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+)
+
+type apiClient struct {
+	baseURL    string
+	httpClient *http.Client
+}
+
+func newAPIClient(baseURL string) *apiClient {
+	return &apiClient{
+		baseURL:    baseURL,
+		httpClient: &http.Client{},
+	}
+}
+
+func (c *apiClient) get(ctx context.Context, path string, out any) error {
+	return c.do(ctx, http.MethodGet, path, nil, out)
+}
+
+func (c *apiClient) post(ctx context.Context, path string, body, out any) error {
+	return c.do(ctx, http.MethodPost, path, body, out)
+}
+
+func (c *apiClient) put(ctx context.Context, path string, body, out any) error {
+	return c.do(ctx, http.MethodPut, path, body, out)
+}
+
+func (c *apiClient) del(ctx context.Context, path string) error {
+	return c.do(ctx, http.MethodDelete, path, nil, nil)
+}
+
+func (c *apiClient) do(ctx context.Context, method, path string, body, out any) error {
+	var bodyReader io.Reader
+	if body != nil {
+		b, err := json.Marshal(body)
+		if err != nil {
+			return fmt.Errorf("marshal request: %w", err)
+		}
+		bodyReader = bytes.NewReader(b)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, method, c.baseURL+path, bodyReader)
+	if err != nil {
+		return fmt.Errorf("create request: %w", err)
+	}
+	if body != nil {
+		req.Header.Set("Content-Type", "application/json")
+	}
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("http request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode == http.StatusNotFound {
+		return &notFoundError{path: path}
+	}
+
+	if resp.StatusCode >= 400 {
+		b, _ := io.ReadAll(resp.Body)
+		return fmt.Errorf("api error %d: %s", resp.StatusCode, string(b))
+	}
+
+	if out != nil && resp.StatusCode != http.StatusNoContent {
+		if err := json.NewDecoder(resp.Body).Decode(out); err != nil {
+			return fmt.Errorf("decode response: %w", err)
+		}
+	}
+
+	return nil
+}
+
+type notFoundError struct {
+	path string
+}
+
+func (e *notFoundError) Error() string {
+	return fmt.Sprintf("not found: %s", e.path)
+}
+
+func isNotFound(err error) bool {
+	_, ok := err.(*notFoundError)
+	return ok
+}