Location sharing: don't hardcode API key

In an effort to make it easier for forks to (a) use their own
API keys (b) change map styles or maybe even providers, move
the MapTiler key out of the source code and pass it in via
env var or property.

Also refactor the utility classes slightly to keep all the URL
related functions together, to reduce the chance of collisions
when maintaining such forks.

.github/workflows/build.yml

@@ -38,6 +38,8 @@ jobs:
         with:
           cache-read-only: ${{ github.ref != 'refs/heads/develop' }}
       - name: Assemble debug APK
+        env:
+          ELEMENT_ANDROID_MAPTILER_API_KEY: ${{ secrets.MAPTILER_KEY }}
         run: ./gradlew assembleDebug $CI_GRADLE_ARG_PROPERTIES
       - name: Upload debug APKs
         uses: actions/upload-artifact@v3

.github/workflows/nightly.yml

@@ -35,6 +35,7 @@ jobs:
         run: |
           ./gradlew assembleNightly appDistributionUploadNightly $CI_GRADLE_ARG_PROPERTIES
         env:
+          ELEMENT_ANDROID_MAPTILER_API_KEY: ${{ secrets.MAPTILER_KEY }}
           ELEMENT_ANDROID_NIGHTLY_KEYID: ${{ secrets.ELEMENT_ANDROID_NIGHTLY_KEYID }}
           ELEMENT_ANDROID_NIGHTLY_KEYPASSWORD: ${{ secrets.ELEMENT_ANDROID_NIGHTLY_KEYPASSWORD }}
           ELEMENT_ANDROID_NIGHTLY_STOREPASSWORD: ${{ secrets.ELEMENT_ANDROID_NIGHTLY_STOREPASSWORD }}