Adjust path for actinia with v3

[mmacata]

History from v1 -> v2:

1. Change URL Prefix in actinia core DONE ✓

2. Find all occurences in code/documentation + Change

• Dokumentation umbenennen api/v1 -> api/v2 ✓
• In response Schema examples umbenennen ✓
• Ideal URL_PREFIX nutzen (actinia_core.core.common.app) ✓
• https://github.com/search?q=org%3Amundialis+api%2Fv1&type=code ✓

3. Occurences DONE: ✓

• mundialis/helm-charts Update actinia version to v2 helm-charts#11
• mundialis/actinia_core Using v2 #277
• mundialis/actinia-stac-plugin Use URL_PREFIX from actinia_core app actinia-stac-plugin#41
• mundialis/actinia-module-plugin Change to actinia-core version v2 actinia-module-plugin#14
• mundialis/actinia-metadata-plugin Use URL_PREFIX from actinia_core app actinia-metadata-plugin#5
• mundialis/actinia_statistic_plugin Use URL_PREFIX from actinia_core app actinia-statistic-plugin#6
• mundialis/actinia_satellite_plugin Use URL_PREFIX from actinia_core app actinia-satellite-plugin#8
• mundialis/ace -> über Umgebungsvariable Add ACTINIA_VERSION with default "v2" ace#7
• actinia-assets actinia-assets/-/merge_requests/142
• mundialis/actinia-gdi -> egal ✓
• QGIS Plugin actiniaconnector/-/merge_requests/5 ✓

Now update from v2 -> v3:

• Check above steps 1-3
• Document list what needs to be adjusted for api version update (as above list was reduced by reusing variables)
• use variables in tutorial / markdown (https://github.com/mkdocs/mkdocs/wiki/MkDocs-Plugins#code-execution-variables--templating)

[anikaweinmann]

For step 3:

• actinia-core
• ace
• actinia_statistic_plugin
• actinia_satellite_plugin
• actinia-assets: mundialis/actinia-assets/-/merge_requests/143
• actinia-example-plugin
• actinia-gdi
• actinia-metadata-plugin
• actinia-module-plugin
• actinia-stac-plugin
• helm-charts
• QGIS Plugin: mundialis/actiniaconnector/-/merge_requests/6