configure rekor signer (v2 for now) with trustroot

[loosebazooka]

Part 1 of plumbing tuf into rekor. I think the only difference between this and the original client is where the url comes from.

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< import com.google.api.client.http.*;
---
> import com.google.api.client.http.ByteArrayContent;
> import com.google.api.client.http.GenericUrl;
> import com.google.api.client.http.HttpRequest;
> import com.google.api.client.http.HttpResponse;
> import com.google.api.client.http.HttpResponseException;
> import com.google.common.base.Preconditions;
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> import dev.sigstore.trustroot.TransparencyLog;
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< import java.util.*;
---
> import java.util.Arrays;
> import java.util.HashMap;
> import java.util.List;
> import java.util.Locale;
> import java.util.Optional;
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< public class RekorClient {
<   public static final String PUBLIC_REKOR_SERVER = "https://rekor.sigstore.dev";
<   public static final String STAGING_REKOR_SERVER = "https://rekor.sigstage.dev";
---
> public class RekorClient2 {
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<   private final URI serverUrl;
---
>   private final TransparencyLog tlog;
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<   public static RekorClient.Builder builder() {
<     return new RekorClient.Builder();
---
>   public static RekorClient2.Builder builder() {
>     return new RekorClient2.Builder();
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<   private RekorClient(HttpParams httpParams, URI serverUrl) {
<     this.serverUrl = serverUrl;
---
>   private RekorClient2(HttpParams httpParams, TransparencyLog tlog) {
>     this.tlog = tlog;
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<     private URI serverUrl = URI.create(PUBLIC_REKOR_SERVER);
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>     private TransparencyLog tlog;
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<     public RekorClient.Builder setHttpParams(HttpParams httpParams) {
---
>     public Builder setHttpParams(HttpParams httpParams) {
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<     /** The fulcio remote server URI, defaults to {@value PUBLIC_REKOR_SERVER}. */
<     public RekorClient.Builder setServerUrl(URI uri) {
<       this.serverUrl = uri;
---
>     /** Configure the remote rekor instance to communicate with. */
>     public Builder setTransparencyLog(TransparencyLog tlog) {
>       this.tlog = tlog;
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<     public RekorClient build() {
<       return new RekorClient(httpParams, serverUrl);
---
>     public RekorClient2 build() {
>       Preconditions.checkNotNull(tlog);
>       return new RekorClient2(httpParams, tlog);
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<     URI rekorPutEndpoint = serverUrl.resolve(REKOR_ENTRIES_PATH);
---
>     URI rekorPutEndpoint = tlog.getBaseUrl().resolve(REKOR_ENTRIES_PATH);
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<     URI rekorEntryUri = serverUrl.resolve(resp.getHeaders().getLocation());
---
>     URI rekorEntryUri = tlog.getBaseUrl().resolve(resp.getHeaders().getLocation());
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<     URI getEntryURI = serverUrl.resolve(REKOR_ENTRIES_PATH + "/" + UUID);
---
>     URI getEntryURI = tlog.getBaseUrl().resolve(REKOR_ENTRIES_PATH + "/" + UUID);
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<     URI rekorSearchEndpoint = serverUrl.resolve(REKOR_INDEX_SEARCH_PATH);
---
>     URI rekorSearchEndpoint = tlog.getBaseUrl().resolve(REKOR_INDEX_SEARCH_PATH);