schema and tests for new table

models/intermediate/cross/schema.yml

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+models:
+  - name: int_daily_currency_exchange_rates
+    description: >-
+      This model holds a lot of data on currency exchange rates.  The time
+      granularity is daily. Each record holds a currency pair for a specific
+      day, source and version.
+
+      Actual rates are source from xe.com data. The `guessed` and `forecast`
+      versions are built by simply 'pushing'  the first/last exchange rate on
+      record. Basically, wherever we dont' have data for a date, we pick the
+      closest actual data point that comes from xe.com.
+
+      Note that, given the dimensionality, getting a simple time series for a
+      currency pair will require a bit of filtering.
+
+      Reverse rates are explicit. This means that, for any given day and any
+      given currency pair, you will find two records with opposite from/to
+      positions. So, for 2024-01-01, you will find both a EUR->USD record and a
+      USD->EUR record with the opposite rate (1/rate).
+    columns:
+      - name: id_exchange_rate
+        data_type: text
+        description: A unique ID for the record, derived from concatenating the
+          currencies, date, source and version. Currency order is relevant
+          (EURUSD != USDEUR).
+        tests:
+          - not_null
+          - unique
+      - name: from_currency
+        data_type: character
+        description: The source currency, represented as an ISO 4217 code.
+        tests:
+          - not_null
+      - name: to_currency
+        data_type: character
+        description: The target currency, represented as an ISO 4217 code.
+        tests:
+          - not_null
+      - name: rate
+        data_type: numeric
+        description: >-
+          The exchange rate, represented as the units of the target currency
+          that one unit of source currency gets you. So, from_currency=USD to
+          to_currency=PLN with rate=4.2 should be read as '1 US Dollar buys me
+          4.2 Polish Zlotys'.
+
+          For same currency pairs (EUR to EUR, USD to USD, etc). The rate will
+          always be one.
+
+          The rate can be smaller than one, but can't be negative.
+        tests:
+          - not_negative_or_zero
+          - not_null
+      - name: rate_date_utc
+        data_type: date
+        description: The date in which the rate record is relevant.
+        tests:
+          - not_null
+      - name: source
+        data_type: text
+        description: Where is the data coming from. Records that are composed from
+          making assumptions on real data will contain `_inferred`.
+      - name: rate_version
+        data_type: text
+        description: The version of the rate. This can be one of `actual` (the rate is a
+          reality fact), `forecast` (the rate sits in the future and is a guess
+          in nature) or `guess` (the rate sits in the past and is a guess in
+          nature). Note that one currency pair can have multiple rate versions
+          on the same date.
+        tests:
+          - not_null
+          - accepted_values:
+              values:
+                - guess
+                - actual
+                - forecast
+      - name: updated_at_utc
+        data_type: timestamp with time zone
+        description: For external sources, this will be the point in time when the
+          information was obtained from them. For stuff we make up here in the
+          DWH, this will be the point in time when we made the assumption.
+        tests:
+          - not_null