  [Abridged] Using the JWST/NIRSpec observations from CEERS we found an extreme
N-emitter, CEERS-1019 at z=8.6782 showing intense NIV and NIII emission. From
the observed rest-UV and optical lines we conclude that it is compatible with
photoionization from stars and we determine accurate abundances for C, N, O,
and Ne, relative to H, finding a highly supersolar ratio log(N/O) =
-0.18+/-0.11, and normal log(C/O) = -0.75+/-0.11 and log(Ne/O) = -0.63+/-0.07,
for its low metallicity, 12+log(O/H)= 7.70+/-0.18. We also analyze other
N-emitters from the literature. All show strongly enhanced N/O ratios and two
of them normal C/O. Massive star ejecta from WR stars are needed to explain the
galaxies with enhanced C/O (Lynx arc and Mrk 996). On the other hand,
supermassive stars (>1000 Msun, SMS) in the ``conveyer-belt model'' put forward
to explain globular clusters (GCs), predict a high N/O and small changes in
C/O, compatible with CEERS-1019, the Sunburst cluster, SMACS2031, and GN-z11.
Based on the chemical abundances, possible enrichment scenarios, compactness,
and high ISM density, we suggest that CEERS-1019, SMACS2031, and the Sunburst
cluster could contain proto-GCs. Finally, we propose that some N-emitters
enriched by SMS could also have formed intermediate-mass black holes, and we
suggest that this might be the case for GN-z11. Our observations and analysis
reinforce the suggested link between some N-emitters and proto-GC formation,
which is supported both by empirical evidence and quantitative models.
Furthermore, the observations provide possible evidence for the presence of
supermassive stars in the early Universe (z>8) and at z~2-3. Our analysis also
suggests that the origin and nature of the N-emitters is diverse, including
also objects like GN-z11 which possibly host an AGN.
