feat: SQL server beta and templates refactoring (#32)

## Description

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At least please give us some description what you are trying to achieve and why your change is needed. -->

relates to #1234

## Checklist

- [ ] Issue was linked above
- [ ] Code format was applied: `make fmt`
- [ ] Examples were added / adjusted (see `examples/` directory)
- [x] Docs are up-to-date: `make generate-docs` (will be checked by CI)
- [ ] Unit tests got implemented or updated
- [ ] Acceptance tests got implemented or updated (see e.g. [here](f5f99d1709/stackit/internal/services/dns/dns_acc_test.go))
- [x] Unit tests are passing: `make test` (will be checked by CI)
- [x] No linter issues: `make lint` (will be checked by CI)

Reviewed-on: #32
Reviewed-by: Andre_Harms <andre.harms@stackit.cloud>
Co-authored-by: Marcel S. Henselin <marcel.henselin@stackit.cloud>
Co-committed-by: Marcel S. Henselin <marcel.henselin@stackit.cloud>

stackit/internal/services/sqlserverflexbeta/instance/datasource.go

@@ -0,0 +1,134 @@
+package sqlserverflexbeta
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+
+	"github.com/hashicorp/terraform-plugin-framework/datasource"
+	"github.com/hashicorp/terraform-plugin-log/tflog"
+	"github.com/stackitcloud/stackit-sdk-go/core/config"
+	"tf-provider.git.onstackit.cloud/stackit-dev-tools/terraform-provider-stackitprivatepreview/stackit/internal/conversion"
+	"tf-provider.git.onstackit.cloud/stackit-dev-tools/terraform-provider-stackitprivatepreview/stackit/internal/core"
+	"tf-provider.git.onstackit.cloud/stackit-dev-tools/terraform-provider-stackitprivatepreview/stackit/internal/utils"
+
+	sqlserverflexbetaPkg "tf-provider.git.onstackit.cloud/stackit-dev-tools/terraform-provider-stackitprivatepreview/pkg_gen/sqlserverflexbeta"
+
+	sqlserverflexbetaGen "tf-provider.git.onstackit.cloud/stackit-dev-tools/terraform-provider-stackitprivatepreview/stackit/internal/services/sqlserverflexbeta/instance/datasources_gen"
+)
+
+var _ datasource.DataSource = (*instanceDataSource)(nil)
+
+const errorPrefix = "[Sqlserverflexbeta - Instance]"
+
+func NewInstanceDataSource() datasource.DataSource {
+	return &instanceDataSource{}
+}
+
+type instanceDataSource struct {
+	client       *sqlserverflexbetaPkg.APIClient
+	providerData core.ProviderData
+}
+
+func (d *instanceDataSource) Metadata(_ context.Context, req datasource.MetadataRequest, resp *datasource.MetadataResponse) {
+	resp.TypeName = req.ProviderTypeName + "_sqlserverflexbeta_instance"
+}
+
+func (d *instanceDataSource) Schema(ctx context.Context, _ datasource.SchemaRequest, resp *datasource.SchemaResponse) {
+	resp.Schema = sqlserverflexbetaGen.InstanceDataSourceSchema(ctx)
+}
+
+// Configure adds the provider configured client to the data source.
+func (d *instanceDataSource) Configure(
+	ctx context.Context,
+	req datasource.ConfigureRequest,
+	resp *datasource.ConfigureResponse,
+) {
+	var ok bool
+	d.providerData, ok = conversion.ParseProviderData(ctx, req.ProviderData, &resp.Diagnostics)
+	if !ok {
+		return
+	}
+
+	apiClientConfigOptions := []config.ConfigurationOption{
+		config.WithCustomAuth(d.providerData.RoundTripper),
+		utils.UserAgentConfigOption(d.providerData.Version),
+	}
+	if d.providerData.SQLServerFlexCustomEndpoint != "" {
+		apiClientConfigOptions = append(
+			apiClientConfigOptions,
+			config.WithEndpoint(d.providerData.SQLServerFlexCustomEndpoint),
+		)
+	} else {
+		apiClientConfigOptions = append(
+			apiClientConfigOptions,
+			config.WithRegion(d.providerData.GetRegion()),
+		)
+	}
+	apiClient, err := sqlserverflexbetaPkg.NewAPIClient(apiClientConfigOptions...)
+	if err != nil {
+		resp.Diagnostics.AddError(
+			"Error configuring API client",
+			fmt.Sprintf(
+				"Configuring client: %v. This is an error related to the provider configuration, not to the resource configuration",
+				err,
+			),
+		)
+		return
+	}
+	d.client = apiClient
+	tflog.Info(ctx, fmt.Sprintf("%s client configured", errorPrefix))
+}
+
+func (d *instanceDataSource) Read(ctx context.Context, req datasource.ReadRequest, resp *datasource.ReadResponse) {
+	var data sqlserverflexbetaGen.InstanceModel
+
+	// Read Terraform configuration data into the model
+	resp.Diagnostics.Append(req.Config.Get(ctx, &data)...)
+
+	if resp.Diagnostics.HasError() {
+		return
+	}
+
+	ctx = core.InitProviderContext(ctx)
+
+	projectId := data.ProjectId.ValueString()
+	region := d.providerData.GetRegionWithOverride(data.Region)
+	instanceId := data.InstanceId.ValueString()
+
+	ctx = tflog.SetField(ctx, "project_id", projectId)
+	ctx = tflog.SetField(ctx, "region", region)
+	ctx = tflog.SetField(ctx, "instance_id", instanceId)
+
+	instanceResp, err := d.client.GetInstanceRequest(ctx, projectId, region, instanceId).Execute()
+	if err != nil {
+		utils.LogError(
+			ctx,
+			&resp.Diagnostics,
+			err,
+			"Reading instance",
+			fmt.Sprintf("instance with ID %q does not exist in project %q.", instanceId, projectId),
+			map[int]string{
+				http.StatusForbidden: fmt.Sprintf("Project with ID %q not found or forbidden access", projectId),
+			},
+		)
+		resp.State.RemoveResource(ctx)
+		return
+	}
+
+	ctx = core.LogResponse(ctx)
+
+	err = mapDataResponseToModel(ctx, instanceResp, &data, resp.Diagnostics)
+	if err != nil {
+		core.LogAndAddError(
+			ctx,
+			&resp.Diagnostics,
+			fmt.Sprintf("%s Read", errorPrefix),
+			fmt.Sprintf("Processing API payload: %v", err),
+		)
+		return
+	}
+
+	// Save data into Terraform state
+	resp.Diagnostics.Append(resp.State.Set(ctx, &data)...)
+}