get reference to next and previous verse in Einzelverssynopse

[flicksolutions]

At the moment we are doing simple math to get the next and previous verse. This doesn't work for edge cases.

presentation_parzival/src/routes/einzelverssynopse/[thirties]/[verse]/+page.svelte

Line 68 in 004b823

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find a solution for this from the full list: metadata-ms-verses.json (in the API)

[pdaengeli]

Test case for this is https://parzival.unibe.ch/parzdb/parzival.php?page=verssyn&dreissiger=257&suffix=30&zusatz=&show=& (and suffix=31, suffix=32) and https://dhbern.github.io/presentation_parzival/einzelverssynopse/257/30 correspondingly, caused by overlong Dreissiger.

Source (applies in similar ways to D, m, n, o, G, I, L, M, O, Q, R, T, U, V, W, Z, Fr21 and Fr69), here Fr21 shown:

         <l xml:id="fr21_257.30">War zvͦ. ditz iſt alſ gvͦt.-</l>
         <l xml:id="fr21_257.31">
            <seg type="Initiale" subtype="Lombarde" n="2" rend="Farbe: rot-blau">D</seg>och næm ich ſelhen blozen lip.-</l>
         <l xml:id="fr21_257.32">Fvͦr etſlich wol gechleidet wip.-</l>
         <l xml:id="fr21_258.01">Do parcifal grvͦz gein ir ſp<choice>

metadata-ms-verses.json:

{"siglum":"fr21","thirties":"256","verse":"29"},
{"siglum":"fr21","thirties":"256","verse":"30"},  <-- normal case
{"siglum":"fr21","thirties":"257","verse":"01"},
{"siglum":"fr21","thirties":"257","verse":"02"},
{"siglum":"fr21","thirties":"257","verse":"03"},
{"siglum":"fr21","thirties":"257","verse":"04"}
--------------------8<--------------------------
{"siglum":"fr21","thirties":"257","verse":"29"},
{"siglum":"fr21","thirties":"257","verse":"30"},
{"siglum":"fr21","thirties":"257","verse":"31"},  <-- edge case
{"siglum":"fr21","thirties":"257","verse":"32"},  <-- edge case
{"siglum":"fr21","thirties":"258","verse":"01"},
{"siglum":"fr21","thirties":"258","verse":"02"}