Allow disabling GPG key editing while leaving signed push enabled

Administrators may choose to populate GPG keys by hand, or to
temporarily restrict adding new keys, without disabling signed push
verification or verification of push certs stored in PatchSets.
Separate the UI and REST API for editing GPG keys from the protocol
machinery for verifying signed push.

Change-Id: I2c921cf92a3452d44ee8cb02efd77ab7f2bd02dd

Documentation/config-gerrit.txt

diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index 42549c8..7472820 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt
@@ -1720,6 +1720,16 @@
 `/Documentation/index.html` can be reached by the browser at app load
 time.
 
+[[gerrit.editGpgKeys]]gerrit.editGpgKeys::
++
+If enabled and server-side signed push validation is also
+link:#receive.enableSignedPush[enabled], enable the
+link:rest-api-accounts.html#list-gpg-keys[REST API endpoints] and web UI
+for editing GPG keys. If disabled, GPG keys can only be added by
+administrators with direct git access to All-Users.
++
+Defaults to true.
+
 [[gerrit.installCommitMsgHookCommand]]gerrit.installCommitMsgHookCommand::
 +
 Optional command to install the `commit-msg` hook. Typically of the

Documentation/rest-api-config.txt

diff --git a/Documentation/rest-api-config.txt b/Documentation/rest-api-config.txt
index c54f7db..b1b795c 100644
--- a/Documentation/rest-api-config.txt
+++ b/Documentation/rest-api-config.txt
@@ -1193,6 +1193,8 @@
 Custom base URL where Gerrit server documentation is located.
 (Documentation may still be available at /Documentation relative to the
 Gerrit base path even if this value is unset.)
+|`edit_gpg_keys`     |not set if `false`|
+Whether to enable the web UI for editing GPG keys.
 |`report_bug_url`    |optional|
 link:config-gerrit.html#gerrit.reportBugUrl[URL to report bugs].
 |`report_bug_text`   |optional, not set if default|