Add indirection for osm providers

To prevent furter breakage of qtlocation osm provider
in existing qt versions, this patch introduces one
level of indirection in resolving OSM providers, fetching
the tile server address from files hosted at
http://maps-redirect.qt.io/osm/5.6/

The content of the files requested for the server
address resolution must be in JSON format, containing
(currently) the following fields:

{
    "Enabled" : bool,  (optional)
    "UrlTemplate" : "<url template>", (mandatory)
    "ImageFormat" : "<image format>", (mandatory)
    "MapCopyRight" : "<copyright>", (mandatory)
    "DataCopyRight" : "<copyright>", (mandatory)
    "MinimumZoomLevel" : <minimumZoomLevel>, (optional)
    "MaximumZoomLevel" : <maximumZoomLevel>,  (optional)
}

Enabled is optional, and allows us to temporarily disable
tile providers if they go offline without firing requests
to them. Default is true.

MinimumZoomLevel and MaximumZoomLevel are also optional,
and allow us to prevent tile requests to the providers,
if they do not support the specific ZL. Default is 0 and
19, respectively.

<server address template> is required, and is the tile
url template, with %x, %y and %z as placeholders for the
actual parameters.
Example:
http://localhost:8080/maps/%z/%x/%y.png

<image format> is required, and is the format of the tile.
Example:
"png" or "jpg"

<MapCopyRight> is required and is the string that will be
displayed in the "Map (c)" part of the on-screen copyright
notice.
example:
"<a href='http://www.mapquest.com/'>MapQuest</a>"

<DataCopyRight> is required and is the string that will be
displayed in the "Data (c)" part of the on-screen copyright
notice.
example:
"a href=
'http://www.openstreetmap.org/copyright'>OpenStreetMap</a>
contributors"

The patch also adds four additional OSM plugin parameters,
modifies an existing ones, and removes another existing one.

Removed:
- osm.mapping.copyright, now removed and replaced by two
other parameters (see below).

New:
- osm.mapping.providersrepository.address, allowing to change
the hardcoded http://maps-redirect.qt.io/osm/5.6/
The implication of this parameter is that it becomes possible
to use file:// urls or even qrc:, allowing to ship custom
providers with the applicarions

- osm.mapping.providersrepository.disabled, allowing to disable
the indirection and go with hardcoded URLs by default.

- osm.mapping.custom.mapcopyright replaces the old
osm.mapping.copyright, and contains the copyright notice to be
displayed next to the "Map (c)" part of the copyright, to be
consistent with the way the copyright notice coming from the
provider data is handled

- osm.mapping.custom.datacopyright replaces the old
osm.mapping.copyright, and contains the copyright notice to be
displayed next to the "Data (c)" part of the copyright, to be
consistent with the way the copyright notice coming from the
provider data is handled

Modified:
- osm.mapping.host now became osm.mapping.custom.host,
improving the naming consistency.

Task-number: QTBUG-54599
Change-Id: Iee88883572a198c00bcf54cf2bc33fbcc0498a68
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>

1 files changed, 20 insertions, 5 deletions

diff --git a/src/location/doc/src/plugins/osm.qdoc b/src/location/doc/src/plugins/osm.qdoc
index 1c924fd3..2fd9e7c4 100644
--- a/src/location/doc/src/plugins/osm.qdoc
+++ b/src/location/doc/src/plugins/osm.qdoc
@@ -60,15 +60,30 @@ a prefix.
     \li User agent string set when making network requests.  This parameter should be set to a
         value that uniquely identifies the application.
 \row
-    \li osm.mapping.host
+    \li osm.mapping.custom.host
     \li Url string set when making network requests to the tile server.  This parameter should be set to a
         valid server url with the correct osm api and the \l{Map::activeMapType} to the corresponding \l{MapType}.CustomMap.
         The CustomMap will only be available if this parameter is set.
-        \note Setting the mapping.host parameter to a new server renders the map tile cache useless for the old custommap style.
+        \note Setting the mapping.custom.host parameter to a new server renders the map tile cache useless for the old custommap style.
 \row
-    \li osm.mapping.copyright
-    \li Custom copryright string is used when setting the \l{Map::activeMapType} to \l{MapType}.CustomMap via urlprefix parameter.
-        This copyright will only be used when using the CustomMap from above. If empty no copyright will be displayed for the custom map.
+    \li osm.mapping.custom.mapcopyright
+    \li Custom map copryright string is used when setting the \l{Map::activeMapType} to \l{MapType}.CustomMap via urlprefix parameter.
+        This copyright will only be used when using the CustomMap from above. If empty no map copyright will be displayed for the custom map.
+\row
+    \li osm.mapping.custom.datacopyright
+    \li Custom data copryright string is used when setting the \l{Map::activeMapType} to \l{MapType}.CustomMap via urlprefix parameter.
+        This copyright will only be used when using the CustomMap from above. If empty no data copyright will be displayed for the custom map.
+\row
+    \li osm.mapping.providersrepository.address
+    \li The OpenStreetMap plugin retrieves the provider's information from a remote repository. This is done to prevent using hardcoded
+    servers by default, which may become unavailable. By default this information is fetched from \l {http://maps-redirect.qt.io} {maps-redirect.qt.io}.
+    Setting this parameter changes the provider repository address to a user-specified one, which must contain the files
+    \tt{street}, \tt{satellite}, \tt{cycle}, \tt{transit}, \tt{night-transit}, \tt{terrain} and \tt{hiking}.
+\row
+    \li osm.mapping.providersrepository.disabled
+    \li By default, the OpenStreetMap plugin retrieves the provider's information from a remote repository to avoid a loss of service due to unavailability of hardcoded services.
+    The plugin, however, still contains fallback hardcoded provider data, in case the provider repository becomes unreachable.
+    Setting this parameter to \b true makes the plugin use the hardcoded urls only and therefore prevents the plugin from fetching provider data from the remote repository.
 \row
     \li osm.routing.host
     \li Url string set when making network requests to the routing server.  This parameter should be set to a