Add raw price feed query (#63)

* Add raw price feed query

* addressed comments

* add blockchain parameter

* add comments

cowprotocol/accounting/price_feed/.sqlfluff

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+[sqlfluff:templater:jinja:context]
+blockchain='ethereum'

cowprotocol/accounting/price_feed/raw_price_feed_query_4252674.sql

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+-- This query parses the raw price_feed table that we sync on Dune,
+-- and returns a view that is based on hourly prices, similar to
+-- how the Dune price feed is used for slippage accounting
+--
+-- Parameters:
+--  {{blockchain}} - network to run the analysis on; currently it only works for mainnet
+--
+-- The columns of the result are
+-- - token_address: a token
+-- - hour: the hour for which a price is computed
+-- - decimals: the decimals of the token
+-- - source: the source from which this price was computed,
+--   price_unit: the price, in USD, of one unit of the token
+-- - price_atom: the price, in USD, of one atom of the token
+
+with imported_prices as (
+    select
+        token_address,
+        cast(replace(time, 'T', ' ') as timestamp) as time, --noqa: RF04
+        cast(price as double) as price_unit_eth,
+        decimals,
+        source
+    from dune.cowprotocol.dataset_price_feed_{{blockchain}}
+),
+
+imported_prices_per_minute as (
+    select -- noqa: ST06
+        token_address,
+        date_trunc('minute', time) as minute, --noqa: RF04
+        decimals,
+        source,
+        avg(price_unit_eth) as price_unit_eth
+    from imported_prices group by 1, 2, 3, 4
+),
+
+imported_prices_per_minute_with_usd_prices as (
+    select -- noqa: ST06
+        ippm.token_address,
+        ippm.minute,
+        ippm.decimals,
+        ippm.price_unit_eth,
+        ippm.price_unit_eth * p.price as price_unit,
+        ippm.price_unit_eth * p.price / pow(10, ippm.decimals) as price_atom,
+        source
+    from imported_prices_per_minute as ippm inner join prices.usd as p on ippm.minute = p.minute
+    where p.contract_address = 0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2 and blockchain = 'ethereum'
+)
+
+select -- noqa: ST06
+    token_address,
+    date_trunc('hour', minute) as hour, --noqa: RF04
+    decimals,
+    source,
+    avg(price_unit) as price_unit,
+    avg(price_atom) as price_atom
+from imported_prices_per_minute_with_usd_prices group by 1, 2, 3, 4