docs(ark): Document ARK URLs for projects (#1408)

* docs(ark): Document ARKs for projects.

* docs(ark): Fix typo.

* docs(ark): Clarify some things.

docs/src/paradox/03-apis/api-v2/permalinks.md

@@ -110,6 +110,28 @@ A Knora ARK URL is intended to be resolved by the [Knora ARK resolver](https://g
 
 For details, see @ref:[Archival Resource Key (ARK) Identifiers](../../05-internals/design/api-v2/ark.md).
 
+### ARK URLs for Projects
+
+The format of a Knora project ARK URL is as follows:
+
+```
+http://HOST/ark:/NAAN/VERSION/PROJECT
+```
+
+`NAAN` is a
+[Name Assigning Authority Number](https://tools.ietf.org/html/draft-kunze-ark-22#section-2.3),
+`VERSION` is the version number of the Knora ARK URL format (currently always 1),
+and `PROJECT` is the project's @ref:[short-code](knora-iris.md#project-short-codes).
+
+For example, given a project with ID `0001`, and using the DaSCH's ARK resolver
+hostname and NAAN, the ARK URL for the project itself is:
+
+```
+http://ark.dasch.swiss/ark:/72163/1/0001
+```
+
+This could redirect to a page describing the project.
+
 ### ARK URLs for Resources
 
 The format of a Knora resource ARK URL is as follows:
@@ -118,6 +140,12 @@ The format of a Knora resource ARK URL is as follows:
 http://HOST/ark:/NAAN/VERSION/PROJECT/RESOURCE_UUID[.TIMESTAMP]
 ```
 
+`NAAN` is a
+[Name Assigning Authority Number](https://tools.ietf.org/html/draft-kunze-ark-22#section-2.3),
+`VERSION` is the version number of the Knora ARK URL format (currently always 1),
+`PROJECT` is the project's @ref:[short-code](knora-iris.md#project-short-codes),
+and `RESOURCE_UUID` is the resource's @ref:[UUID](knora-iris.md#iris-for-data).
+
 For example, given the Knora resource IRI `http://rdfh.ch/0001/0C-0L1kORryKzJAJxxRyRQ`,
 and using the DaSCH's ARK resolver hostname and NAAN, the corresponding
 ARK URL without a timestamp is:
@@ -143,6 +171,13 @@ The format of a Knora value ARK URL is as follows:
 http://HOST/ark:/NAAN/VERSION/PROJECT/RESOURCE_UUID/VALUE_UUID[.TIMESTAMP]
 ```
 
+`NAAN` is a
+[Name Assigning Authority Number](https://tools.ietf.org/html/draft-kunze-ark-22#section-2.3),
+`VERSION` is the version number of the Knora ARK URL format (currently always 1),
+`PROJECT` is the project's @ref:[short-code](knora-iris.md#project-short-codes),
+`RESOURCE_UUID` is the resource's @ref:[UUID](knora-iris.md#iris-for-data), and `VALUE_UUID`
+is the value's `knora-api:valueHasUUID`.
+
 For example, given a value with `knora-api:valueHasUUID "4OOf3qJUTnCDXlPNnygSzQ"` in the resource
 `http://rdfh.ch/0001/0C-0L1kORryKzJAJxxRyRQ`, and using the DaSCH's ARK resolver
 hostname and NAAN, the corresponding ARK URL without a timestamp is:

docs/src/paradox/05-internals/design/api-v2/ark.md

@@ -25,7 +25,7 @@ License along with Knora.  If not, see <http://www.gnu.org/licenses/>.
 
 Knora must produce an ARK URL for each resource and each value. The ARK identifiers used
 by Knora must respect
-[the draft ARK specification](https://tools.ietf.org/html/draft-kunze-ark-18).
+[the draft ARK specification](https://tools.ietf.org/html/draft-kunze-ark-22).
 The format of Knora’s ARK URLs must be able to change over
 time, while ensuring that previously generated ARK URLs still work.
 
@@ -66,8 +66,8 @@ http://HOST/ark:/NAAN/VERSION/PROJECT/RESOURCE_UUID[/VALUE_UUID][.TIMESTAMP]
   Example: `20180528T155203897Z`.
 
 Following the ARK ID spec, `/`
-[represents object hierarchy](https://tools.ietf.org/html/draft-kunze-ark-18#section-2.5.1)
-and `.` [represents an object variant](https://tools.ietf.org/html/draft-kunze-ark-18#section-2.5.2).
+[represents object hierarchy](https://tools.ietf.org/html/draft-kunze-ark-22#section-2.5.1)
+and `.` [represents an object variant](https://tools.ietf.org/html/draft-kunze-ark-22#section-2.5.2).
 A value is thus contained in a resource, which is contained in its project,
 which is contained in a repository (represented by the URL version number).
 A timestamp is a type of variant.
@@ -84,9 +84,15 @@ The `RESOURCE_UUID` and `VALUE_UUID` are processed as follows:
 2. Any `-` characters in the resulting string are replaced with `=`, because
    `base64url` encoding uses `-`, which is a reserved character in ARK URLs.
 
-For example, given the Knora resource IRI `http://rdfh.ch/0001/0C-0L1kORryKzJAJxxRyRQ`,
-and using the DaSCH's ARK resolver hostname and NAAN, the corresponding
-ARK URL without a timestamp is:
+For example, given a project with ID `0001`, and using the DaSCH's ARK resolver
+hostname and NAAN, the ARK URL for the project itself is:
+
+```
+http://ark.dasch.swiss/ark:/72163/1/0001
+```
+
+Given the Knora resource IRI `http://rdfh.ch/0001/0C-0L1kORryKzJAJxxRyRQ`,
+the corresponding ARK URL without a timestamp is:
 
 ```
 http://ark.dasch.swiss/ark:/72163/1/0001/0C=0L1kORryKzJAJxxRyRQY